Time Frame: Mukuro has been released out of Vendicare Prison so it would be after the Shimon Arc. The Arcobaleno Arc did not take place here. This will happen in the 5th Harry Potter series but situations might be tweaked around from the other books. It is 5 years after that Shimon Arc so Tsuna is now 19 and the rest, you can calculate it yourselves.

The stories I see on this crossover are usually slash and very little adventure/action ones in the HP world. Even if there were, they're mostly incomplete... so I thought I'll write one myself. Therefore, no pairings since I want the focus to be adventure but if you squint, there might be some hints along the way. Lastly, please review and give some criticisms to help me mold this story into an enjoyable one. Plus they make me look forward to writing quicker.

Disclaimer: I do not own Katekyo Hitman Reborn or Harry Potter. I might also be taking bits and pieces from the books as well.

Chapter 1: The Exchange

"Why have we been called back?"

"I don't know. What do you think he'll want to do?"

"What is our next step now that the Dark Lord has returned?"

Uncertain discussions could be heard from the occupants of the table back in Malfoy Manor where the masked men gathered. Even with their masks covering their facial features, their whispering voices betrayed their nervousness. Many of them rubbed their wrists absentmindedly as their tattoo burned. They had been called once again to gather through the Dark Mark that was imprinted on their wrist.

And they did not know why.

All of a sudden, the doors of the room opened and in walked a cloaked man, accompanied by the owner of the house and his wife. The room immediately fell silent as they watched the cloaked man move to the head of the table. He then sat down slowly, his scarlet eyes observing each and every one of his followers who did not dare to look back at him.

"You know how to decorate your place well Lucius… Come, to my left." The man spoke up, breaking the silence as he indicated to his left.

Nodding his head, Lucius Malfoy moved towards the empty seats with his wife in tow. The atmosphere was uncomfortable and the members in the room fidgeted. The Malfoys had managed to secure seats beside the Dark Lord, which meant that they were now in favor. The eyes of the Death Eaters watched Lucius and his wife move towards their seats and soon fell on the man at the head of the table. Not having the chance to look at their lord properly as compared to the time they had gathered in the graveyard but now that they could, they gulped.

The man had lost his human features ever since the last time they saw him thirteen years ago. His face no longer possessed of the original handsome traits but instead, his skin was pale-white and in place of his nose were snake-like slits. In short, it resembled a skull.

"Welcome my friends. It has been some time after we have met at the graveyard. I hope that you are well… no? I sense unhappy faces under those masks of yours… Not welcoming of my presence here are we?" The head of the table asked, sending cold shivers down everyone's spine; his voice was soft but held a tinge of amusement. "…Gibbon?"

The said Death Eater startled slightly as he was addressed directly by the man, "N-No, my lord."

The cloaked man continued to stare at him before finally looking away while Gibbon breathed heavily – he was one of the few that did not search actively for the lord after his downfall and he thought that he would be dealt with severely but it appeared that the lord was in a rather good mood. The Dark Lord breathed in deeply and gave a crooked smile.

"Nevertheless, now that I've returned, I want to fully put my plan into operation, I want to know the full prophecy, as well as to kill Harry Potter."

Murmurs were heard from the people surrounding the speaker as no one had knew of the plan the man had. When did he ever have the chance to execute his plan?

"My l-lord, p-plan? We're not aware of any plans." One of the Death Eaters dared to ask.

"No, none of you are aware of this plan, other than me… and another. It was formulated a long time ago and it has been progressing smoothly. It will be in action; it's about time…" Lord Voldemort spoke softly before the edges of his lips curled.

"Time to start Phase Two."

"Are you sure about it?"

A voice sounded through the office. A man sat behind the Headmaster's desk, his face worried as he received the news. Shocked voices came from the portraits of former Headmasters and Headmistresses that were hanged around the room as they feared for the safety of their Hogwarts student.

"Yes, I'm very sure of it. I've been to the meeting. The Dark Lord had already taken action without us knowing. Dumbledore, the boy is in great danger now." The informant mumbled quickly to the wizard.

"This is not good; we have to seek help as soon as possible. I'll reconvene the Order of the Phoenix as fast as I can. We must protect Harry Potter at all costs. Speaking about that, I have someone in mind whose organization would be strong enough to aid us…" The wizard called Dumbledore interlocked his fingers and rested his head on them. He then closed his eyes and pondered on the possibilities on how to engage that someone but he could only think of one way.

"Severus, get me an owl that is strong enough to fly to Italy; I do hope that the offer is still valid." He asked of the man who had supplied him the information at the start but before the Potions Master could speak, someone else beat him to it.

"Wait, Dumbledore, Italy?" A woman asked, knowing instantly what was in Italy. "Are you sure we are going to do that? I mean, they aren't wizards and as we all know, we in the Wizarding world have a long-term feud between us, and the Mafia. We have been fighting for many years now. What makes you think that they will be willing to help us? Moreover, how can you be sure that they are not on You-Know-Who's side?"

Dumbledore gave a sigh. "Minerva, there is no other way is there? You heard what Severus had said. We'll need a stronger force and they're our best bet since their organization is larger than ours. Moreover their organization has been the most powerful Mafia Famiglia in all of Italy and it will prove to be wise to try to get their help."

"We must gather as many allies as possible and I'm quite certain that Voldemort is well-aware of the feud to not approach them yet without something attractive in return. However, we will beat him to it because we have something that the mafia wants, something that their First Boss entrusted to us, something that was the root cause of the feud in the first place."

A pause. "A Mirror."

"The Mirror of Erised?" The ever-sharp witch asked, the first object that came into mind. No one knew how the Mirror ended up in Hogwarts 400 years ago but now that Dumbledore explained the situation, everything clicked for the female Head of Gryffindor House.

"Precisely. The Mirror has been safe with us for a long time now, as according to the First Boss' wishes, and I believe it is time for it to be returned to their original owners in exchange for help."

"But wouldn't they –"

"I know what you are implying; I won't rule out the possibility of them being hostile to us like the previous bosses but we must take our chances. This matter is too serious to be treated of lightly. Furthermore, the organization has changed their ways after the Second Boss and are on the way to becoming the vigilante group they were in the first place so I believe that I can trust them now. I believe that I can trust Timoteo." Dumbledore peered above his half-moon spectacles, his blue eyes twinkling brightly as he looked at the defeated face of the female Professor – she would respect the wizard's decisions.

"Then I shall proceed to carry out your instructions?" Severus tried to confirm the Headmaster's intentions.

"Yes, please do. And send it straight to their Boss, will you? In Vongola Headquarters."

Nodding his head, the Potions Master left the office while Dumbledore and Minerva watched the end of his cloak disappear round the corner.

It was not an everyday routine that he could sit back and relax but now he could – he had a competent handler to help him take care of his paperwork. Timoteo leaned back on the sofa at the side of his office and closed his eyes, enjoying the moment of peace before a voice called out to him.

"You didn't even realize that I walked in here. What would happen if it was a hitman after your life?"

Without opening an eye, Timoteo chuckled. "A hitman won't be able to make it this far, not with you here with me Reborn." He peeked at the corner of his eye, just in time to see a baby with a yellow pacifier hanging around his neck smile and shake his head in amusement.

"Care to have Espresso with me, the Ninth?" He offered to the retired Vongola Boss who accepted with another chuckle. This instead, was one of the routine activities that Timoteo did whenever Reborn decided to pop in.

The bright sun shone into the office where the two of them drank and chatted. The drifting of the clouds in the sky made the atmosphere serene while the quietness of the mansion made it a perfect situation to have a nice, peaceful break, something that all Vongola Bosses would have wanted and… he had it.

"How is young Tsunayoshi doing now?" Timoteo sipped his drink and asked in passing, wanting to know how the young man was coping now that he was the acting Boss.

"No different from five years ago. He's still that No-Good Tsuna." Reborn replied curtly while the Boss laughed heartily.

"I hope that I'm not burdening him with that huge amount of work…"

"I'm sure he's coping well – I'll see that he'll finish those work for you. That's also part of his training to becoming a better boss." A twinkle in the Sun Arcobaleno's eyes meant that Tsunayoshi wouldn't be having any rest soon; the infant would make sure of it.

"Don't force Tsunayoshi too hard. After all he did take the initiative to offer to help me with my work–" The retired Boss was suddenly interrupted by a loud tapping on the glass pane of his balcony. Immediately on instinct, Reborn pointed his Leon-turned-gun at the person, or in this case an owl, ready to protect the Vongola Boss.

"Wait, that owl… It can't be…" Something was nagging Timoteo as he continued to watch the tawny owl tap its beak on the glass. If it was from other Families they would use the official bird messenger so the possibility of them sending a letter to him through owls was null.

"This is from the other world isn't it?" Reborn frowned as he wondered what they needed.

"I'm having this suspicion that it is… let me see what they wrote." The man got up from the sofa and walked towards the door, sliding it open. The owl instantly flew towards the Boss and perched on his outstretched arm. Timoteo detached the letter that it was entrusted with before walking out to his balcony. Upon seeing that its job was done, the owl gave a low hoot before taking off into the distance.

The man pursed his lips as he moved towards his desk slowly. Reborn watched him as he read the letter, his eyebrow quirking every few seconds. "It's from the other world. They need our help, and they are willing to return that object that Primo had entrusted them with. It must be something very important for them to have to exchange that item they have been holding on for a long time," Timoteo finished reading the letter and turned to Reborn.

"…This doesn't sound good, does it Reborn?"

"No... They had not given up that object even though many of them were killed when the previous Bosses went after it, but now that they are willing to give it up on their own, it must be something serious." The Sun Arcobaleno shadowed his eyes under his fedora. "We have been without conflict with their world for quite some time now and to be involved in this, you know what might happen do you? It could mean further trouble for the Vongola."

"Yes, I'm aware of the consequences but there's nothing much I can do... We must also take into consideration that Primo had asked them for help in the past and it is perfectly reasonable for them to ask us for help now in return. And I know that Primo would want to return them the favor… Although reluctant, we must respect his wishes and since I have passed on the legacy to Tsunayoshi, he must do it... Reborn, will you continue to aid him in this quest? I doubt it will be that easy to restore stability between our worlds and this could also be the chance to amend our ties."

"As you wish, Vongola Nono." Reborn bowed slightly as the old man nodded his head a fraction. He picked up his prized pen and wrote something on a separate parchment of paper. He then placed the original letter together with his own into an envelope and stamped on the document, sealing it with his Dying Will Flame.

"Good luck, Tsunayoshi…"

Knock knock.

Silence greeted the visitor but the visitor knew better – his Boss was still in the room, doing his paper work as the scribbling of the pen and shuffling of papers could be heard. Knowing that the Boss ignored the knock on purpose, the visitor decided to speak up.

"Tenth, it's me. I know that you've instructed that no one was to disturb you but this is urgent."

"Gokudera-kun," The man mumbled, "It's alright. Come in."

A silver-haired man opened the door on the command and walked into the office of the Vongola Decimo. As he walked in, the Vongola Boss took a quick glance before returning back to his work. His Storm Guardian was wearing his suit, complete with a red tie that was tucked in and it was unusual for him to do do so. Gokudera wearing that formal could only mean one thing. He had just returned from the meeting that the previous Boss had held as his representative since the Tenth had been too busy for the past few days to even leave his office.

"Are you alright, Tenth? You have been working non-stop ever since we returned back to Italy." The 3/4 Italian man asked with concern.

"I'm fine, just that I wanted to finish this as soon as possible without distractions. Anyway, how was the meeting?" The Vongola Tenth asked as he leaned back into his leather seat and finally took a break. He stretched his body before ruffling his brown hair, yawning ungracefully unlike a proper boss.

"Tenth! You are the greatly respected Boss! You should be well-aware of your manners!" Gokudera hurried over and whipped out a comb from nowhere and immediately groomed the man, much to his dismay.

"G-G-Gokudera-kun! There's no one here except us!" The Boss laughed as he pushed his Guardian away. That man had not changed at all! "So what brings you here? You said it was urgent."

Gokudera nodded his head and picked up the briefcase he had put down before the grooming incident. He unlocked the case and Decimo saw a flicker of a Sky Flame in it. Glancing at the content inside the briefcase to ensure that everything was proper, the Storm Guardian then presented the entire briefcase to him.

"A letter has been forwarded to you by Vongola Nono and it's extremely confidential. We can't touch it at all, only you can."

The Boss was surprised; he had received missions from the Ninth but never had he received any officially confidential mission from him. Moreover, the letter was protected by a Sky Flame so that no one else other than a Sky Flame user could have touched it which was very rare for him to do so. Picking up the letter gently, the Sky Flames slowly died down.

"This is definitely weird. Let's see…" His heart feeling uneasy, the Boss opened the letter and scanned through the contents. He frowned after almost every line as Gokudera watched on silently, not wanting to distract his Boss' concentration. Decimo then glanced through the other letter attached before he closed his eyes and gave a heavy sigh.

"T-Tenth, is something wrong?"

"Gather all the Guardians. Abandon whatever mission they have on their hands and meet me at the meeting room." The Vongola Boss opened his eyes slowly, his voice grave as he stared at the letter once more.

"We have an urgent mission, direct orders from the Vongola Ninth."

Knowing that it was serious, Gokudera immediately nodded his head and left the room, following the man's orders. The Decimo put his palm on his forehead and massaged them, trying to crease the frowns that had formed as he sat alone in silence.

"Sawada is sure edgy to have me cancel all of my missions! I EXTREMELY demand an explanation!" An over-enthusiastic white-haired man hunched over his briefcase which was filled with lots of documents, his body raring to get into action. Sasagawa Ryohei was always active, just like the sun, the sun that shines brightly upon an area.

"Maa, maa Senpai! I'm sure that Tsuna has a good reason to do so." A tall and cheerful man put his hands at the back of his head and chuckled at his teammate. Just like the tranquil rain, Yamamoto Takeshi was always the calm one who will settle conflict and wash them away.

"Lambo-sama wants to return back to my sleep. What does No-Good Tsuna want?" A cow-like boy scratched his black puffy hair, drawing attention to himself. His eyes drooped sleepily as his nap time was affected.

"Kufufufu~ If Tsunayoshi summoned us here without a proper reason, I'm going to kill him and take over his body once and for all~" A purple-haired man with a creepy red right eye appeared out of nowhere, with another similar looking girl beside him. As the mist cleared, it was revealed to be Rokudo Mukuro and Dokuro Chrome, the two illusionists who were able to create something from nothing and nothing from something.

"If that herbivore wastes my time, I'll bite him to death." A raven-haired man stood alone at the corner of the room with his hands crossed over his chest, not willing to crowd. The lone wolf, Hibari Kyoya was the aloof and drifting cloud that protects the Family from an independent standpoint, and whom nothing can ever bind.

"Fufufu~, our dear Cloud Guardian still can't control his temper hmm?" Mukuro mocked the said man who glared piercingly at the male Mist Guardian, their feud obviously still not forgotten. "No wonder you lost to me…"

That was it. To remind the skylark of his humiliating defeat was to court death.

"I'll bite you to death!" The raven-haired man moved forward swiftly, brandishing his tonfas just as the illusionist materialized his trident. Metal met metal as the two Guardians exchanged moves. Switching back and forth between attacking and defending, the fight became more and more violent till it was not safe for anyone to be standing still in the room. Picking up Lambo, Ryohei leapt out of the way while the other two Guardians scattered as they were almost hit as well.

"You almost hit us! That was extremely dangerous!"

"O-Oi! Stop fighting!"

"Mukuro-sama!"

Persuasions by the Guardians to stop fighting proved to be futile for the two continued their fight. The clashing of the weapons increased as the fighting Guardians decided to up their attacks by adding in their Dying Will Flames.

"Enough!" The great door to the meeting room slammed open, revealing the Vongola Decimo and his right-hand man. Both the Mist and the Cloud Guardians merely stared at the intruder with distaste that their fight was interrupted. The Boss did not speak any further but continued to stare at them with his caramel eyes. Feeling the odd aura he was giving out, Hibari and Mukuro turned away from one another, keeping their weapons. They knew that something was amiss; Decimo's eyes were sharp and solemn, even though he was not in his Hyper Dying Will Mode. Giving a last glare to each other, the two Guardians returned to their assigned seats and folded their arms.

Sighing, Sawada Tsunayoshi signaled to the rest of his Guardians to sit as he walked towards the head of the table. The Sky Boss waited for his Guardians to fully settle down before taking in a deep breath, thus commencing the emergency meeting.

"I apologize for having this meeting out of nowhere and I know that many of you are unhappy with the sudden decision to cancel your missions on hand, but there is a reason for it. I have received a letter from the previous Boss and he has given his direct orders for every Guardian to be involved in it due to its severity." Tsuna produced the letter and placed it carefully in the middle of the table as the rest watched the Sky Flame flicker continuously on the document.

"Gokudera-kun has planned your assignments in this mission according to your skills and abilities and I have approved them, so I do not expect any arguments about your duties, are you clear?" The authoritative tone that was seldom heard in the Boss' voice put everyone on the alert.

Silence answered the speaker and taking it as a cue that no one would interrupt him, Tsuna started on revealing the details of the mission. Occasional nods were given as he explained; several frowns were seen on the Guardians' faces. Finally, they got to the most important point – their main motive... was to guard a boy named Harry Potter in a school of Witchcraft and Wizardry from this man called Voldemort.

"A what school? Witch and Wizard?" The 10-year-old Lambo asked once more as he thought that he heard wrongly.

"That's right Lambo, witches and wizards. A magic school," The Tenth nodded at the cow-boy before he was asked with another question by his Storm Guardian.

"Harry Potter? That doesn't sound like an Italian name, neither does it sound Japanese. And Voldemort sounds retarded." Gokudera added on while Tsuna inhaled deeply as he tried to cover up his smile – indeed, who would call himself a name as weird as Voldemort?

"Because it isn't. It's a British name and therefore, you should have deduced where this mission would be taking place." Tsuna smiled as he watched the faces in the room change with recognition.

"…England," Yamamoto thought aloud.

"Scotland to be precise," Tsuna nodded to his Rain Guardian, "Now I want to make several things clear before I give out your assignments. We will be working together under Vongola so I expect each and every one of you to be on your best behavior, no exceptions."

"The next thing to note is that this mission is only confidential to our Family only. No one else is allowed to know any details of this mission, which means not even the CEDEF. Everyone clear?" The brunette asked and received nods and murmurs from all Guardians except Ryohei, who was circling his thumbs and looking the other way. He knew what his Sun Guardian was thinking – about his sister, but they did not have a choice. It was the Ninth's decision and they must follow it.

Swallowing hard, the Boss asked once more, "Onii-san? I need your word."

"…Crystal clear." The boxer took in a deep breath and nodded his head firmly. As long as his sister would be safe.

Tsuna smiled gently at the man before starting his instructions once more, his eyes determined now that he was assured that his Family would be supporting him all the way. "All of you are given specific positions and I know that you will do your part well."

"Rokudo Mukuro," He addressed the male Mist Guardian. "I have decided to send you undercover to this place called the Ministry of Magic where you will gather information and pass it on to us through Chrome. I'm sure that you are already an expert judging from the fact that you have done it before," Tsuna gave a small chuckle as he related to the Millefiore case, "If that's alright with you and Chrome?"

"No problem, Boss." Chrome answered softly.

"Kufufufu~ Tsunayoshi. I don't like the tone you are ordering me around but I must admit, I did have fun being undercover so I don't mind doing it again…" Mukuro gave a creepy grin before dissipating into thin air, leaving purple mist in his wake.

"Yamamoto," Tsuna then turned to his Rain Guardian who sat up straight, ready to receive his part. "I need you to get to this place immediately. Something tells me that that the attack on this boy will be soon and you are the best candidate for it..." The man slid a piece of paper to Yamamoto and shook his head as his Hyper Intuition began to bug him.

"Consider it done, Tsuna!" The man gave a thumb up as the Storm Guardian looked on grudgingly.

"Gokudera-kun," The silver-haired man went stiff in attention, "I need you to prepare a jet for our transportation but prepare Yamamoto's first. I'll pass you the details later on. And I will also need your help with some registration problems." Tsuna nodded his head as he gave a smile to his Storm Guardian and like always, Gokudera glowed brightly upon being relied on.

"Yes Tenth! I will do it as though it depended on my life!" He thumped his fist on his chest enthusiastically as Tsuna sweatdropped at the huge amount of enthusiasm the man was giving out.

"Lambo... Err... You look tired… Uhm… You can return back to sleep. I'll inform you when I've... decided on your part." The brunette trailed off and chuckled uneasily. He did not want to involve the still-a-child boy in a dangerous mission like this but he had no idea what the Lightning Guardian would hear of it.

"Huh? Nothing for me? Okay I'll go back to sleep... You No-Good Tsuna better compensate with the Great Lambo with sweets later on!" With that said, the cow-boy slid out of his chair and tottered to the door, yawning as the Vongola Decimo sweatdropped once more. One was too over-enthusiastic while the other was too under.

"Onii-san, you'll be on standby with me when the boy needs help, which I reckon would be soon." He next looked at the Sun Guardian as the white-haired man pumped his fist into the air, agreeing with it.

"Lastly, Hibari-san... I'll discuss with you your part of the mission after this so..." Tsuna started but was interrupted by the Cloud Guardian.

"Herbivore, I'll bite you to death for making me crowd for no good reason."

"Wait! Your part consists of better parts... And maintaining order!" The Tenth waved his hands frantically in front of him and sighed when Hibari relaxed on hearing the last part.

"Tell me now..." He demanded.

"Okay, okay! Before that, I hope that all of you will take precaution here. I don't want anyone of you to get hurt." Tsuna's eyes softened as he looked at his Guardians. "Take care and may we make this mission a success." The Boss nodded his head at each of the Guardians who were still seated in the room.

"...With that, meeting is over."

One by one, the remaining Guardians filed out of the room while Tsuna and Hibari remained seated, waiting to be left alone to discuss about their deal. The Boss noticed that his Storm Guardian was taking an awful long time to pack up his stuff and knew that he did not trust the skylark enough to leave the two of them alone. Tsuna chuckled slightly, shaking his head and Hibari glanced at Gokudera, his patience waning.

"Herbivore, you're packing up too slowly. Stop wasting my time and get out of here." Hibari yawned while the silver-haired man glared at him, muttering curses under his breath.

"Gokudera-kun," A call to his name made the Storm Guardian shift his attention back to the speaker, "When you leave, please close the door after you."

Before Gokudera was about to argue back that the Cloud Guardian was not safe to be alone with, he held his tongue as he saw the smiling face of his Boss. The face that understood his Guardians.

The face that was full of trust that Hibari would not hurt him in any way.

The Storm Guardian knew that he was defeated and that he could not change the Boss' mind and he huffed - his Boss would be able to defeat that ex-prefect anytime he wanted to. Understanding the Boss' intent, he nodded his head and proceeded to the door. Stepping out of the room, Gokudera gently pushed the door shut.

With the click, it was just Tsuna and Hibari alone.

"Now that we are alone, let us begin…"