A/N: Hello again! This is in the same universe as my other KHR fics but it can be read as a stand alone. Enjoy!

"As the leader of the Teens Unite Club, I hereby call this meeting to order!"

"Who made you the leader, Lambo? I was the one who started this club so I should be the leader!"

"Actually, since I'm the oldest one here, I should be the leader."

"That's enough! Lambo-sama has more important things to attend to today than your silly bickering! We need to come up with a plan of action!" Lambo slammed a palm down onto the table with dramatic flair. Back straight, head high and flames crackling on the surface of his skin, he knew he was meant to be the leader of this three man club.

Ipin huffed while Fuuta sighed in resignation. The two knew Lambo well enough to know this wasn't a matter worth fighting over. Lambo's stubbornness and need for attention always won in the end. The three were huddled up in the club meeting room located on the first floor of the Vongola mansion right next to the kitchen. There was easy access to food and hardly anyone except servants came by this way which made it a good place for the TUC to scheme.

"We tried forcing some sort of self-enlightenment moment during the Piercing Catalyst but we underestimated how oblivious Tsuna-nii can be. Even Fuuta's candidate from his list of 'Top Mafia Bosses That Could Steal Tsuna's Heart' couldn't hold Tsuna-nii's attention long enough to force a civil war in Vongola during The Dance. We need something more obvious! Something straightforward to make Tsuna-nii make up his mind and just choose somebody! More importantly, Lambo-sama needs him to choose Reborn."

"Oh please, you obviously don't know Tsuna-nii as well as I do! Tsuna is a sentimental and simple guy. He will definitely choose Kyoko-nee-san." Ipin was all about girl-pride at this age, you see.

"You two are just lucky I was fair enough not to rank this. My money's still on Dino-san. He has this big brother persona that's so calm, kind, reliable and relatable. Tsuna-nii would want to settle down with a boss too, for sure." Fuuta crossed his arms and leaned back. He was confident in the win after all.

It's been almost a year and a half since they started the bet called 'Tsuna's Pick'. Who would Tsuna-nii end up choosing? When money was involved, they got serious.

At first, Fuuta was really sure it was going to be either Hayato-nii or Takeshi-nii because they were the ones who spent the most time with Tsuna. Reborn had always been the top pick for Lambo but there was a time where Lambo had almost changed his choice to Kyouya-nii because Reborn went away for a few months and Tsuna relied heavily on his cloud for directions. Ipin had switched between Haru, Kyoko and Chrome a couple of times. Mukuro had always been a wild card and they had agreed that if Mukuro was chosen, they would split the pot evenly and start over again if necessary.

"We need to make it straightforward. Like forcing Tsuna-nii to write a definite name down or something." Ipin suggested.

"It's not like we can go up to Tsuna-nii and ask him to choose someone from the family though." Lambo pointed out.

"What if we phrase it like 'who would you choose to be life partners with if you had to choose someone?'" Fuuta continued. They were getting somewhere. They huddled closer, feeling a plan starting to form.

"That's too obvious. Tsuna-nii's intuition would tell him we've got money on his decision."

"We need to go at a slightly more roundabout manner."

"If we make it roundabout, he might get all oblivious again. You've seen how those plans worked out!" Fuuta sighed in exasperation. In fact, all three of them were getting exasperated at their boss.

"We just need to find a way to ask him to choose someone in a non-aggressive manner." Lambo turned to look at Ipin. "How can we do that in a manner that suggest we're just harmless teens, Ipin?"

There was silence for a few minutes before Ipin shot up in her chair as if she was struck by a moment of genius.

"Oh my gosh. I've got it." It wasn't even an exclamation. It was more of a declaration that the boys had better be prepared to bow down to her amazing intellect. "Soul marks."

"Soul marks?" The boys echoed.

"Yes. Soul marks are the in thing now, haven't you heard?" Ipin's eyes had turned all innocent as if her statement was a fact. "Everyone is doing it nowadays!"

"What are soul marks?" Fuuta asked, curious, while Lambo just groaned.

"Ipin, you read this in some fan fiction didn't you?"

Ipin harrumphed. "Fan fiction is a good source of information and it generates creativity, okay? Any way! Here's how it's going to go…"

'`~~OooOooOooOooOooOoo~~'`

"Soul mark?"

"Tsuna-nii, you've never heard of a soul mark? It's the in thing right now!" Ipin recited as practiced. "See? The trend nowadays is to write the name of the person who you think is your soul mate on your wrist." Ipin turned her right wrist over to show Tsuna what was written.

"G-Dragon? Who's that?" Tsuna used his thumb to trace the script along little Ipin's wrist. She had used a black marker to ink it across her wrist just below where the palm starts in a neat, simple handwriting.

"He's just the dreamiest singer ever! I believe he is my soul mate because he's just everything I've ever dreamed of in a life partner and we would get married and we would be perfect for each other! Don't you have someone like that too, Tsuna-nii? A person of the opposite gender who you've always dreamed of being together with? Someone who would make the perfect wife?" Tsuna felt like he should know who Ipin was hinting at but surely someone as innocent as Ipin wouldn't be hinting at anything right?

"An idol? Psssh Ipin please." Lambo pushed Ipin aside. "That's never going to happen. Your soul mark should be the name of someone who challenges you. A soul mate should be someone who's been your rival or a strong force of influence in your life. See who I have, Tsuna-nii!" Lambo thrusted his left wrist into Tsuna's view and there, in a messy scribble with black ink was the name 'Reborn'. Tsuna swore he heard Ipin mutter something like 'way too obvious' or something but he wasn't too sure.

"I wrote Reborn's name because Reborn was the one I needed to beat since I was young and Reborn was the reason I am who I am now. That's why Reborn is the name I chose as I believe that Reborn is my soul mate." Tsuna was pretty sure that Lambo had repeated Reborn's name way too many times. Nah, he must be overthinking things.

"Tsuna-nii! See who I've got!" Fuuta called out and Tsuna's attention turned to him. It was starting out as a strange day but he could get past this. The teens were always weird every now and then. It must be a phase. "I've written your name Tsuna-nii! I believe you're my soul mate because you're a boss that I can look up to! You've been the perfect older brother to me and I'm always learning new things from you, Tsuna-nii. You're reliable and warm and everything an older brother and boss should be. That's why I feel like you're my soul mate."

"That's so sweet, Fuuta." He gave a genuine smile and Fuuta smiled back. It was really sweet of them to be doing this. He was just glad that at this age they didn't pick up bad habits like smoking (from Hayato) or brawling (from Kyouya). Tsuna gave thanks once every couple of days none of them turned out anything like Mukuro.

"You should join us, Tsuna-nii!" Lambo excitedly handed him a black sharpie. "If you were to choose someone to be your soul mate, who would it be?"

"Someone to be with for eternity! Someone who matches your soul!" Ipin added.

Tsuna paused for a moment to think about it. Soul mate? Soul mates are usually life partners that compliment you perfectly in every way, right? Maybe he shouldn't think too hard about this since the kids weren't being too serious about their choices as well.

I mean, come on.

"Well, I would probably choose-"

"Tsuna-nii! Think about it carefully! You have to treat this as if it were a permanent marking! That's the whole purpose of having a soul mark. And you have to wear it until the ink fades out. That's the rule!" Ipin insisted.

"Fine…" Well. At least today would be interesting.

'`~~OooOooOooOooOooOoo~~'`

"Who did you write, Tsuna-nii?"

Tsuna turned his wrist over, obviously proud of his choice because duh, it was just so very obvious who his soul mate was!

"Natsu? Natsu!? Tsuna-nii, you can't choose something that isn't even human!" Ipin groaned in frustration and Fuuta had face-palmed.

"But Natsu and I are soul mates! We sgare our flames and he's my partner!"

"You have to have a human as your soul mate, Tsuna-nii. Your soul has got to have another soul of equivalent value."

"Fine…"

'`~~OooOoo~~'`

"I've got it this time."

"Whose name did you write, Tsuna-nii?" Lambo asked. The aniticipation between the three teens was palpable.

"It's a human right?" Ipin asked, not trusting Tsuna's judgement since an animal was chose previously.

"It is." Tsuna replied. He was confident he got it right this time. Lambo grabbed his hand and turned it over revealing a black script just below Natsu's name which was stroked through with a line.

"Oh my gosh." Lambo groaned.

"Seriously, Tsuna-nii, you're not getting the point of a soul mark." Ipin chasticed while Fuuta's face showed clear disappointment.

"What? Did I do it wrong again?" Tsuna was clearly confused. "Giotto and I must share a little bit of our souls or something since he's my ancestor and we look so alike."

"I'm not even going to try to logically challenge that statement." Fuuta stepped aside and pushed Ipin forward to deal with it.

Ipin held on to both his hands and looked him in the eyes and a slight smile on her face. "Tsuna-nii, just… write the name of someone who is alive, ok?"

"Fine…"

'`~~OooOoo~~'`

"And this time, your choice is human?"

"Yes."

"And alive?"
"Yes." Tsuna rolled his eyes. He wasn't daft. He knew what he was doing. The kids were treating him as if he were dumb or something. He turned both wrist over this time.

"Tsuna-nii! I didn't know you were into threesomes!" Ipin squealed, fan-girl mode activated.

"Byakuran would be top, of course, and Uni would be the bottom." Lambo analysed the names on both of Tsuna's wrists and nodded in understanding.

"What? Huh? Why would Byakuran be top? Top of what?" Tsuna wasn't too sure how being soul mates would head to an assignment of position. "I would think that the three of us would be equals in this since we are part of the Tri-ni-set."

"Oooo! Equals in threesomes are pretty hot too!" Ipin nodded excitedly in approval.

"Wait a moment." Fuuta was eyeing him suspiciously. "Let me get this clear. You chose Byakuran and Uni because they're part of the Tri-ni-set, didn't you?"

Tsuna nodded with an innocent smile. "It would make sense that they would be my soul mates, wouldn't it? I'd like to think the universe chose the three of us as equals in terms of our soul."

The three kids groaned in unison and Tsuna was beginning to feel as if he'd disappointed them or something.

"Tsuna-nii." Fuuta took a deep breath as if he was mentally preparing himself to explain something highly complicated. "A soul mate is someone who would complement you in every single way. Someone who you want to spend the rest of your life with."

Tsuna frowned. "Like I said, I chose Uni and Byakuran because it's obvious the universe had placed us together."

"Yeah, but do you want to spend the rest of your life in close proximity to them?"

"Well…"

"Do you want to spend your days with Byakuran?"

"No."

"Pick someone else then!"

"Fine…"

'`~~OooOoo~~'`

Tsuna woke to someone scratching along his forearm.

"Reborn?" Crap. Reborn had caught him sleeping on the job. "I was just resting my eyes, I swear! I'll get back to work now." Tsuna straightened himself up on his chair and looked down at the last document he was working on before exhaustion had claimed him.

"Why are all these names scribbled and cancelled out on your arm?" The hitman still hadn't let go of his left arm. Reborn was trying to scratch off the ink but it only made his skin turn red in irritation.

"The kids were trying to teach me about soul mates and soul marks."

"And you decided on Natsu? Byakuran?" Tsuna was sure he heard a 'Tsuna you're an idiot' in the subtext.

"They weren't really good at explaining what a soul mate was."

Reborn gave a quite snort. "My name isn't here."

"Huh?"

"Baka-Tsuna. Have you decided?"

"Huh?" Reborn gave him a look that meant he was losing patience.

"Have you decided on a name?"

"No." Tsuna sighed. "They looked so disappointed every time I tried to reason my choice. I've been thinking about who would fit the whole 'Soul Mate' description, and there are so many who fit bits and pieces of it. That's why I have all these names." Tsuna gestured to his left arm which was filled to the elbow with black ink, then showed his right arm which was filled with similar but more illegible writing. There were almost twenty names – a line through them all because the kids did not approve of his justifications of the names. He didn't even know why he was trying so hard to please them but this matter seemed really important.

At one point, he had written the names of all seven of his guardians because it didn't feel right to single just one of them out. Upon looking at the list of names, he felt the need to include the rest of his famiglia which included the girls, Dino, and Basil. He had considered the Varia members – Xanxus in particular, because they were somewhat equal in soul value, right? Tsuna was so very confused about what the kids were expecting from him.

"Baka-Tsuna, don't hurt your brain." The hitman teased but it only made Tsuna smile. Tsuna knew Reborn well enough by now to hear the subtle 'you don't have to try so hard to please everyone'. He had worked long enough with his tutor to understand the underlying messages often hidden beneath bard insults.

"It just seems so easy for them to decide who their soul mate is, and yet it's been so difficult for me! I keep thinking about the famiglia because everyone means so much to me. How do I choose just one person among everyone I love?" He really didn't mean to spill his thoughts to his devil hitman advisor.

Reborn had a blank look on his face and Tsuna wasn't sure if it meant 'you're an idiot', 'do not bore me with such mundane problems', or 'are you seriously having a heart to heart session with me?'.

And also, was Reborn going to let go of his arm?! Tsuna tried tugging it back but Reborn wouldn't let go. It did pull the hitman out of his trance and Reborn settled with a flat stare which clearly meant 'you're an idiot' – a look that Tsuna was very familiar with by now. To Tsuna's surprise, Reborn tossed Tsuna's arm aside to pick up the black sharpie resting on the table – the same one Tsuna had been using to write the names on his arm.

"Baka-Tsuna, listen carefully because I'll only explain this once." Reborn scribbled something on his own left wrist, capped the sharpie, and quickly stuck his left hand back into his jacket's pocket before Tsuna could catch a glimpse of what was written. Tsuna then felt a sharp tap on his forehead where Reborn had used the sharpie to strike him to get his attention back, away from whatever mysterious thing Reborn had just written. Reborn's eyebrows were raised and his lips were quirked in a manner suggesting the hitman was humouring him.

Then, all of a sudden, Reborn went into full tutor mode. "A soul mate is someone who complements you in every way. What that means is that they are perfect for you. Their soul draws your soul closer – so close that you find yourself unable to continue living without this person after having met them." Reborn's eyes held an intensity that Tsuna only saw when there was a serious matter at hand. "You would feel that this person owns you – builds you up on good days and tears you down on bad days. There should be no one else that can fill the void of this person – no one else who means the same, no one else who can do the same thing they can do to you.

"There are many you would die for, but your soul mate is someone you die with." Reborn leaned towards Tsuna and suddenly Tsuna felt as if all the space around him was being consumed and the only thing that existed was this force of a hitman surrounding him. There was something heavy in the air. He had never seen Reborn so serious before. Tsuna's throat felt dry and his hands were clammy.

Reborn continued: "Your soul mate is someone who goes through the highs and lows, and still remains as the constant. Someone who stands apart from everyone else because that's how special a soul mate is – one and only. Someone who is not below you, someone who isn't above either. Your soul mate is someone who challenges you and supports you from a position right next to you." Reborn inched even closer and slipped something into Tsuna's open palm, sending a jolt of current through him. Tsuna grasped the familiar width of the sharpie on his hand, eyes never leaving Reborn because he simply couldn't look away. His intuition was blaring a message, headlining that this was an important moment that Tsuna needed be alert about because of the clear sincerity and honesty pouring out of the entity across him.

The familiar deep voice of his advisor broke the silence once again. "Who is that to you, Tsuna? You don't have to think hard."

The man was right. He didn't need to think hard. The image of his soul mate had started to form as Reborn explained it to him and now there was a clear picture – a single name. As Tsuna removed the cap of the sharpie, he hurriedly tried to find a space to put the name down – the name that suddenly held so much importance and value, the name he didn't think of until now but it was oh so obvious! It was the name he really needed to have on his arm to show that he had decided. However, in his search he realised that there wasn't any space left on his arm and so Tsuna tried to roll up his sleeves but they wouldn't go up any further. Fuck. He needed to put this name down. There was a charge of seriousness in the air and his intuition was telling him this was something important that he needed to prove immediately.

"You've been so focused on the famiglia that you didn't leave any space for you soul mate." Reborn taunted but the bitter sadness rang sharply in Tsuna's ears.

"Reborn." An apology unsaid.

"I still haven't told you the most important thing about soul mates."

There was more? Tsuna stopped his search. Stopped moving, stopped breathing because what this man had to say was more urgent and important. "What is it?"

"A soul mate bond goes two ways." It was an obvious statement, one that surprised Tsuna because he never thought of it that way! His eyes quickly darted to Reborn's, needing to understand more about what Reborn was trying to say. The intensity in Reborn's eyes, however, immobilised all thought. "You complement your soul mate just as they complement you. You are perfect for them. You have the power to build them up or tear them down. They would die without you – they would die with you."

Tsuna felt he was suffocating. His heart was beating like crazy. What the fuck was going on? What was Reborn trying to say? The underlying message was clear but Tsuna couldn't process it at the moment.

"And do you know what the most important sign of a soul mate is, Baka-Tsuna?" Reborn removed his left hand from his pocket and used it adjust his fedora while his other hand combed through black spikes. For the first time, the light caught onto a black script on the hitman's pale wrist and Tsuna's eyes locked onto it, never losing sight of until it disappeared back into the jacket's pocket. He would never forgot the sight of it on Reborn.

"Just like you bear your soul mate's name, they bear yours too."

And just like that, Tsuna understood what it meant to have a soul mate – that someone was chosen to be yours just as you were chosen to be theirs. The fact that Tsuna could choose who his soul mate was, and that he had been picked in return, made being soul mates even more significant.

The fact that the greatest, deadliest hitman in the mafia had the words 'Ba-ka-Tsu-na' in hiragana written across his wrist as a declaration – Reborn chose him! – made his brain crash and his heart soar.

"Reborn, I-"

"Baka. Tell me when you find some space there for a soul mate." Reborn turned to leave the room, clearly done with the conversation.

"Reborn!" Tsuna felt the need to confirm something.

The hitman paused, listening.

"Soul mates are for life, right? They don't change?" Tsuna challenged.

"They don't." With that, Reborn left.

Tsuna smiled, heart at peace and mind at ease, and went back to his work. He would deal with Reborn later. He was good at reading Reborn's silent messages.

It said "Take your time. I'm your's whenever you choose to be mine."

And that's how Tsuna understood the significance of a soul mark.