Disclaimer: I could never claim for any of these two fandoms as mine. I'm merely a fan with an imagination and a thirst for writing fanfiction for both of them.

Warning: Spoilers ahead!

Assassination Classroom: Vongola Style!

Chapter 1. Yamamoto Takeshi

10/07/15

It was with a grin so simple and honest that they first met him. A hand lifted in a friendly greeting and a tenure full of positive energy. Nagisa smiled together with the whole class.

Such a refreshing greeting, he remembered thinking to himself.

He was tall, happy and friendly. That's what everyone thought of Yamamoto Takeshi. There were no doubts, no suspicions… nothing. He was simply accepted. He was an honest-to-goodness all-around nice guy who's always ready to give anyone and everyone a smile.

He failed the exam for transfers and landed on Class E. He gets bad grades like the rest of the class but if given the chance, he could pass exams without much problem. But he didn't seem to care much with grades. He could have gotten himself transferred to the main campus but he said he liked Class E that's why he stayed.

He was odd and a goofball. He gets along with everyone, especially with Sugino. And by extension, to him as well. His best friend finally have someone to play and talk about baseball without being afraid of being put down. Nagisa chuckled to himself. A day wouldn't pass without the two not bringing up anything baseball-related.

When it came to baseball, those two were like obsessed fanboys. That exhibition game between Class E and the baseball team was like a zesty festival for the two. They couldn't believe Yamamoto-san's fast balls, at all! They were very, VERY fast. And he could hit Shindo's fast balls like a pro! Well, considering he could hit even Koro-sensei's fast balls sometimes, it shouldn't have surprised them much. Though he thought Sugino was a little jealous of Yamamoto-san's talent in baseball; especially when Yamamoto-san had admitted getting scouted by the Pro League at one point. But that had been easily resolved when Yamamoto-san took notice of this and told his fellow baseball enthusiast, "Maa, Sugino. Not everyone grows the same way. You're just a late bloomer. Like Tsuna!"

They didn't know who Tsuna was but Sugino looked better after that. And that was all that mattered then.

All-in-all, Yamamoto-san blended in the class so easily that it was hard for anyone to suspect anything wrong with him at all. Though there was that one time he stared at Kayano and suddenly commented, "You should smile lively for real."

Kayano's eyes widened for a second but smiled and nodded the next. The topic was dropped and forgotten thereafter. It was weird, but it wasn't important enough to contemplate over.

Even when they try to assassinate Koro-sensei, he was always the to-go guy if you're looking for someone to help you out. Yamamoto-san never really initiated assassinating Koro-sensei himself, but he was always forthcoming if he was asked to help. He didn't complain nor ask much questions other that what he was expected to do. He'd do anything with a grin worthy of a toothpaste commercial.

His gun handling was average and he was a bit good with the knife but he wasn't really comfortable with them. Unless he was using the knife for sushi, Yamamoto-san once said. He's agile, got great reflexes and his movements were smooth and confident but he always seem to move as if the knife was longer, with a better reach. Karasuma-sensei inquired about this once and Yamamoto-san said he wished it was a sword, a katana to be more specific. When asked why, he simply smiled and answered easily, "I'd know how to use it better. It's just like a baseball bat."

Sugino laughed and patted Yamamoto-san's back at that. While Karasuma-sensei sighed but promised to try acquiring one for him. Some in class expressed interest with using a sword as well but Karasuma-sensei warned he wouldn't be able to teach them beyond some basic moves. Most deflated at that, it wouldn't be of much use against a super being that could move at Mach 20 if they couldn't use it beyond the most fundamental of skills. Even so, Yamamoto-san insisted he still wanted one. Karasuma-sensei just shrugged and gave his okay.

Yamamoto-san was strange but alright. There was nothing suspicious about him, at all. At least, on a normal day-to-day basis, that was.

During times of tension or crisis, his smile turned sharp and his eyes were focused and intense. Not many took notice of this though since they were all occupied to a degree during these circumstances. But of those who did, it was intriguing to say the least. Nagisa felt calmer and at ease at this change for reasons he couldn't figure out. Karma said it made him wary. Koro-sensei turned more attentive to Yamamoto-san, glancing more often to the tall teen than necessary. Karasuma-sensei looked conflicted. And Bitch-sensei was contemplative.

The first time this happened was when they first met Takaoka-sensei. It was only by chance that Nagisa witnessed it. He was the nearest to the taller teen that time. He just suddenly felt a quiet, dangerous aura beside him for a moment and his eyes shifted immediately to his side, only to see it gone the next second. It happened so fast, he thought he imagined it. But Yamamoto-san seemed willing to play along with Takaoka-sensei amiably and well-enough but had refused the cakes.

Yamamoto-san wasn't present the next day, he said he was needed back home. When asked what it was, he said there was a family event he couldn't miss. And they left it at that. He always seemed to just skip school for some family event every now and then, so, they've gotten used to it.

But for Nagisa, he felt it was better that Yamamoto-san wasn't present that day. Things might have gone differently if he were, whether it was for better or worse, he couldn't tell for sure. But it wouldn't have been pretty. The baseball enthusiast wasn't one to care for petty insults and the degrading comments that the main campus had turned to their class in a regular basis but Nagisa could guess that he was the type to not let anyone who'd physically hurt his friends go even when things seemed to have gotten resolved.

The second time was during their summer retreat to an Okinawa resort. It was the first time Nagisa seen the tall teen without a smile. Yamamoto-san gazed at their ill classmates with a quiet and calm visage as if silently vowing he would fix it, somehow for whatever means necessary. It was somewhat reassuring, Yamamoto-san's determination, that was.

It was when they first encountered Smog that they first saw – briefly as that had been – when Yamamoto-san used the sword Karasuma-sensei gave him. It had been a month ago when Karasuma-sensei distributed the anti-sensei swords and attempted to teach it to them, but it didn't work out, at all. There was little to nothing they could do with it, so, they gave up trying to use since then. Most just left it somewhere to gather dust but Yamamoto-san carried it with him all the time, along with a shinai in a baseball bat's bag. They never saw him did some practice with it, so, they were surprised when he finally took it in his hand – assured and at ease.

They didn't know when exactly he moved but they were sure it was when Fuwa was giving her explanation for Smog's suspicious actions. Before Fuwa started talking, Nagisa briefly saw Yamamoto-san put his hand on the shinai until Koro-sensei turned his gaze to him. It looked like they were talking through their eyes. It was surreal.

He didn't know what happened next with those two because his attention had shifted to Fuwa. But the next thing they knew, Yamamoto-san was already behind Smog and had knocked him out with his anti-sensei sword.

They happily praised him and patted his back but Yamamoto-san wasn't happy about it. When they asked why, he answered, "Because I should have moved before Karasuma-sensei got hit by the poison."

Everyone just simply reassured him that he wasn't at fault. Everyone hadn't expected Smog at all and wouldn't have known anything was wrong if Fuwa hadn't said anything about it. Everyone had been busy reassuring Yamamoto-san that no one questioned how and why he knew to be suspicious of Smog.

The first time he saw Yamamoto-san's serious, calculative gaze was when they met Grip in that hallway. His stance was stiff and ready to move while his hand had stayed on his shinai's hilt. It was also the first time some sort of suspicion was laid on Yamamoto-san. When Grip called them out of hiding, it seemed he'd missed Yamamoto-san's presence. Grip had been so surprised when they left their hiding place. They thought the surprise came from his miscalculation but, somehow, Nagisa doubted it. Grip's eyes steadily gazed at Yamamoto-san's form like he was trying to remember him from somewhere.

Even when Grip was fighting Karma, his gaze would wander back to Yamamoto-san as if fretting for any sudden, fatal movement. That never happened though, since Karma defeated Grip through his wits and cunning.

They defeated Gastro after that but Yamamoto-san hadn't done anything special. Though Koro-sensei did specifically called to him to not use "his sword" and simply follow his instructions. Koro-sensei may have thought Yamamoto-san would sneak behind Gastro the same way he did to Smog. That would have been dangerous. Gastro has a gun and he had such superb marksmanship. Not to mention the assassin's uncanny ability to just know about his ambushers.

The first time they felt an inkling to his bloodlust was when Takaoka-sensei blew up the antidotes for their ill classmates. But Nagisa's own bloodlust and declaration of his want to kill Takaoka-sensei held their attention more prominently. So, most forgot about this and were simply relieved when all things were over.

The next time Yamamoto-san let out his bloodlust though, everyone felt it surely and clearly. And it was really frightening.

Yamamoto-san had been away for a few days for some family event again and was due to be back in class just a day after the Shinigami walked in their class so casually and naturally before he threatened Bitch-sensei's life were they not to comply to his demands. He wasn't there that time but he had returned to town that evening and immediately went together with Koro-sensei and Karasuma-sensei when they've called him and asked about his classmates' whereabouts. Yamamoto-san had apparently stubbornly and vehemently protested against not coming that both their teachers could only reluctantly agree to his insistence.

When Karasuma-sensei went off to chase the Shinigami, Yamamoto-san immediately knocked out Bitch-sensei with the hilt of his shinai. He then turned to them, asked them to stand back and took a stance with his shinai. And the strangest thing happened. He slashed the shinai to the metal bars like they were paper and had moved so gracefully like he'd been handling the sword for years!

They all looked at him with wide eyes – stunned but awed. When they looked at his hand, the shinai was gone and had been replaced by a REAL, really sharp katana. And when they finally seen his eyes, fear seemed to have encompassed the whole class. They were really cold and hard. No one said it, but everyone had realized then and there that Yamamoto Takeshi wasn't an ordinary student. He's a professional like Bitch-sensei, those three assassins back in Okinawa, Lovro and the Shinigami.

A flash of hurt briefly sparked through Yamamoto-san's eyes as he watched them before he turned his back, ready to give chase to Karasuma-sensei and the Shinigami. Before he could leave though, Koro-sensei spoke, "Do you have a Family?"

It was a peculiar question but they all got the gist that the family Koro-sensei was asking was far from the domesticated one they're familiar with. Though Yada seemed to understand the most of what it meant, mostly due to her enthusiastic learning from Bitch-sensei.

It was that sort of thing. They soon understood that Yamamoto-san was from that world. The same world Bitch-sensei had lived her life in – the dark side of society.

Yamamoto-san turned back to them. Gone was his cold visage. And with a warm smile, gentle eyes and soft tune, he answered while fingering a ring secured to his neck by a necklace, "They're a wonderful family, Koro-sensei. It was my choice so don't worry about it."

It was around that time that Bitch-sensei came back to consciousness and gasped as she looked at the ring so attentively and fixatedly. Her face paled, her eyes widened, and her body shook. Bitch-sensei was afraid. And they understood that the ring was important, and Yamamoto-san was important and to be feared in the underworld.

Everyone tensed and carefully watched Yamamoto-san's every movement. Everything else seemed to have faded to the background.

What would he do? Why was he here? Who sent him? Was everything a farce? Questions circled their minds endlessly.

Until Koro-sensei simply laughed and gone was the tension that easily. It was also then when they've taken notice of Karasuma-sensei and the Shinigami had fallen off a pit from above. And Yamamoto-san had immediately moved in. He weaved in and out of combat easily. There wasn't anyone there who'd dare question Yamamoto-san's skill in the sword. To say he was great was an understatement. Even the Shinigami seemed to have acknowledged his abilities.

Between Karasuma-sensei and Yamamoto-san, the Shinigami didn't have a chance. Not even Koro-sensei intervened at that point. Not even when the Shinigami fired the gun embedded inside his hand! Because Yamamoto-san was immediately in front of the Shinigami and easily cut the bullet in half while Karasuma-sensei knocked him out from behind.

There was a moment of unsure silence after that. Karasuma-sensei and Bitch-sensei talked for a bit about her betrayal but everyone forgave her easily enough. And the atmosphere lightened immediately. Until Karasuma-sensei finally asked about Yamamoto-san's skill in the sword.

"Oh, that?" Yamamoto-san grinned his usual grin while he casually held his katana to his side and it reverted back to being a shinai and proudly admitted, "My Old Man taught it to me more than two years ago. It's the Shigure Soeen Ryu. It's the best sword style there is. It's invincible!"

And just like that he was back to the kind and carefree Yamamoto Takeshi they met the first day. They weren't as trusting as they were to him thereafter but they slowly warmed up to him after a time. He still acted the same and he was genuinely having fun with them. He didn't mention anything about what his Family was but he'd openly tell them stories of some crazy, unbelievable things he and his family had gone through. And it would always leave them laughing to tears.

He only ever did use his Shigure Kintoki, his katana, once when Shiro and Shinigami – or Koro-sensei's apprentice, he supposed – showed up. That was a really dangerous event that he didn't want to think about if possible. It gave him nightmares for so many nights. And he doesn't believe he'd ever forget about it for the rest of his life!

But Yamamoto-san did continually use his anti-sensei sword instead. He even started attacking Koro-sensei out of the blue thereafter. He could cut down two or three tentacles at times but Koro-sensei always seemed to be able to escape before Yamamoto-san could deal some fatal damage.

Lovro was incredibly impressed the first time he'd seen this. When he'd managed to corner Yamamoto-san, Lovro's face when he heard his name and sword style was a mixture of fear and awe. It seemed that the sword style was quite infamous. But Lovro didn't spoke a word anymore of this subject. When Bitch-sensei and Lovro conversed next, everyone noticed how more fixated they looked at Yamamoto-san. At times, the two would tremble from an illusory chill as Yamamoto-san gazed back at them.

That had not been reassuring. But everyone moved on from this and simply accepted it. Yamamoto-san was still nice and warm to them. He never tried to attack them and would come to their rescue if something was wrong. Their doubts vanished from that point.

Then, on that final day. That day they finally were able to kill Koro-sensei, right after Koro-sensei had said his final words to everyone he turned to Yamamoto-san silently asking for something they knew had to do with Yamamoto-san's other life.

"Don't worry, Koro-sensei. Tsuna would always pull us through and does his best to protect everyone, the same way me and the rest of the family does to everyone. And if there ever came a time any of them-," Yamamoto-san's eyes panned over them, "-were to get dragged into that world.-" A wave of complete stillness enveloped the whole area as Yamamoto-san's eyes hardened with determination, "-I promise I'd take care of them and Tsuna would welcome them with open arms. Tsuna would never make anyone do anything they don't like. Right, Tsuna?"

"Of course," an unknown voice echoed through the field. As one, they all looked at the source and found an unassuming – though short – young man, leaning against a tree. His brown locks gently danced with the breeze and his eyes, the colour of sunset, gazed kindly but reassuringly back to Koro-sensei, "You've taken care of Takeshi so well this past year. It's the least I could do. Though it would, of course, be better if they never have to find their way there."

Koro-sensei and the brunet silently gazed at each other until their teacher nodded his head the best he could from his laid out form. Koro-sensei and Yamamoto-san trusted the brunet and that was enough for them as well.

Yamamoto-san grinned so brightly then, "So you can take a rest now, Koro-sensei, and let your students take care of themselves."

Koro-sensei let out a laugh they've all been used to and closed his eyes, "And with this, the last term of fundamentals is now over. Good luck, my students! Always remember, make an assassination Sensei would be proud of."

A/N: Well, tell me if there were anything wrong with it. Grammar or facts from either fandom, or even with my characterization. Feel free to criticize it. I'm writing Tsuna's version next, still in Nagisa's POV. I'll have it done soon, I believe. So, leave all your thoughts in your reviews~!

PS: For those who read HI:DES and PEx, both are in a temporary hiatus. I'm not discontinuing them, I just won't be able to write for either of them right now. My laptop broke and all my plans and world building were in my laptop and I'm in a loss. Until I get my laptop fixed or until I get a hold of myself (whichever comes first), those two would be in a hiatus. In the meantime, please enjoy this series of one-shots for my first crossover for two of my most beloved fandom.

Ciao!