Disclaimer: I don't own Katekyo Hitman Reborn!

Summary: AU!TYL and AU!Flames Addiction. Reborn realizes that, like the Guardians, he suffers from Flames Addiction. More importantly, he discovers that it isn't accidental but rather, purposeful.

Characters: Adult Reborn, Tsuna.

Pairing: R27

Rating: T

Warnings: This is not fluffy, at all. There is no angst either. It's dark-inclined. This love (because yes, they are in love despite or maybe because of) is twisted in some way. Cravings will make you think of drugs, or at least, some of the possible effects drugs have, so it is a reference to drugs addiction (duh).

This is the beginning of an unhealthy relationship too. If someone speaks like Reborn does in this, run away. Yeah, Reborn is very much dark, here, in a I relish in torturing people and killing them slowly, it's my purpose in life kind of way.

Here, there is an effect of Tsuna's fear of abandonment that turns him into Manipulative!Tsuna as early as childhood. While he is manipulative, he isn't evil or overly dark, but his good heart isn't pure.

Genre: Romance. Can be perceived as slightly (or a lot) horrifying.

Length: One-shot.

A/N: By the way, they're both possessive in this. Though I can't seem to decide which one is the worst.

Hope you'll enjoy nevertheless!

It took him too long to notice. It had taken him over ten years to suspect that something was wrong. It was almost humiliating, considering the pride he had in his unmatched skills. He was sharp, had always been, or otherwise he would have already been dead. His power of observation was considered as such, getting the nickname of 'Mind Reader' even before he began to claim that he was one. Nothing escaped him. Nothing.

And yet, he had missed it since the beginning.

Reborn entered the office silently, attention completely focused on the brown-haired figure behind the desk, working on paperwork. Bright honey-colored eyes glanced at him inquisitively, wordlessly asking him about the reason of his coming. His Sky Flames were humming as always around him, invisible but noticeable. Tsuna paused in his signing at Reborn's gravity and put down his pen, observing his mentor.

The hitman didn't say anything. He felt his Sun Flames brush eagerly with the Sky Flames, his core purring contentedly at the radiating Harmony. His fingers stopped twitching where they were hidden in his pockets, relaxing. His back lost its stiffness as a sigh fought its way out of his lungs. He held it in, dark eyes shadowed by the fedora fixed on Tsuna. His mood lightened up considerably with simply being with the twenty-something-year-old Sky, soothing his murdering urge and his thirst for blood and death.

By basking into Tsuna's presence, Reborn completely changed, almost fully dropping his guard. He didn't. He was still a killer, an experienced killer with harsh expectations, so he refused to allow a moment of weakness. He was the best out there, and yet, he hadn't noticed.

"When did you realize?"

Despite the lack of context, Reborn could see by the flash of recognition in Tsuna's eyes, that the Decimo had understood. He smiled pleasantly, a smile that was usually reserved for neutral Families still hesitating in following Vongola to soothe them and convince them.

"You'll need to be a bit more specific, Reborn. Are you asking me when I realized that there was something in me that cause the others to bully me? Or are you asking me when I realized that I could control it?"

"Both."

Tsuna, still pleasant, put his elbows on the desk and let his chin rest on his joined hands, observing the hitman. He wasn't considering lying to the hitman. It was pointless, even more so now that the Sun had finally understood.

"I knew that something was probably wrong with me years before you came to me." Tsuna started to explain, unfazed by his curious phrasing. "I caught on less than two years after the bullying began. To be fair, I have never been the sharpest tool in the box, especially with my Flames Sealed. I suspected that there was a reason for the bullies to always come back, aside from the fact that I was an easy prey, so I started to experiment a bit. I quickly learnt that, while I was hated and treated worth than trash, people couldn't ignore me. Some even sought me out, like Mochida."

He tilted his head to the side.

"Of course, I didn't really understand back then. I just figured that there was something in me that attracted people and caused them to be violent, with their fists or with their words." He shrugged. "I was kind of resigned to it since I couldn't find anything to make them stop. I didn't know the real origin of the problem, so, how was I supposed to solve it?"

"And then, I came with all the answers you needed." Reborn reflected. "The Dying Will Bullet had been the trigger."

Tsuna's smile morphed into an amused grin, finding humor in the accidental pun, and nodded.

"Dying Will Mode had started to give me some clues. I grew aware of my Flames after that. Thinking that I had found the origin of my problem, I started to experiment a bit. The first time, I went a bit overboard."

"Gokudera." Reborn's face was blank as he remembered the mood swings of the Storm.

"I had, by accident, worsened his temper, from his aggressiveness to his ability to trust." Tsuna confirmed "Hayato's behavior was extreme in his youth, his Flames instantly latching to mine to soothe their craving for acceptance and home. His actual personality is the real one." He paused thoughtfully, adding. "That is, if you ignore his cravings. I am to blame for those."

"Everyone was fair game." Reborn clarified, thinking about Yamamoto who had also had a similar reaction.

"The most difficult had been Mukuro and Kyouya. One because of his distrust and the other because of his wish for independency."

Tsuna got up, ruffling some of his papers. "As you continued to teach me, I got better at exploiting the Harmony factor of my Flames without manifesting them. It isn't surprising, since my Flames had been leaking out of me even before you chipped the Seal. The difference is that I could control them."

Reborn shifted, leaning against the wall beside the door.

"When I noticed that people kept flocking to me with or without your input, I started to use my Flames as subtly as I could."

"Why didn't I remark it?" The hitman mused. "From what you're saying, you've been doing it from almost the beginning."

Tsuna widened his eyes and tilted his head to the side, slightly frowning and peering at him in concern.

"Doing what?" He asked with a bewildered voice, the epitome of innocence.

Anyone walking in at this exact time would fall for it. In fact, anyone would fall for it at any time, even the Guardians or Reborn – had he not been there for the entire discussion. His mind flashed to Nana's obliviousness.

"I see." He commented flatly.

Tsuna's look vanished as he gave the hitman a cheeky grin.

"I'm a good actor, I learnt from the best after all."

Reborn knew that he was referring to both Nana and himself. He crossed his arms on his chest, mentally flapping through memories. Tsuna seemed to read his mind.

"I knew since the beginning that there was something wrong with you, Reborn." He admitted as he scrunched up his nose. "I started to understand when I noticed that my Flames didn't have a lot of effect on you, not like with everyone else. For a long time, I wondered if it was because you were a hitman, if you were a Sky or if you were just too strong." He put his papers in different piles. "My theories were thrown to the ground when Xanxus showed signs of being affected, as well as his Guardians. So I kept wondering. Why weren't you reacting? Why weren't you saying anything? Was it possible that you hadn't noticed something so big despite appearing omniscient?"

"It had to do with the Curse, hadn't it?"

"Your Flames were caged." Tsuna stilled in his movements, observing the hitman. "They didn't feel very alive, you know? Except when you actively used them via Leon, otherwise, they were stuck in immobility. Thinking about it now, I am not surprised that you couldn't sense mines as my Guardians could. How could you possibly have when they were dying?"

They stared at each other for a few minutes, Tsuna patiently waiting for Reborn to finally ask the questions that had been plaguing him for the past weeks. He knew that he was taking liberties that the hitman would have punished anyone else for. He did it because he also knew that Reborn wouldn't attempt anything. It was already too late.

"There's more than curiosity about your Sky attribute to lure Elements inside their sphere." Reborn pointed out. "If it was only that, you would have stopped after Bonding with your current Guardians. There was no need to exploit outrageously your Harmony to develop addictions in your Elements' cores and ensnare the Varia." As well as the Arcobaleno and to a point, Enma and his Elements. "Why are you still feeding their cravings?"

Tsuna blinked, genuinely surprised. Wasn't it obvious?

"Because they're mine." He answered as if it was evident. "Because I was a lonely child who had only known verbal and physical abuse from kids, teachers and later on, my own mother. Because I knew that if I seized the opportunity, I could have friends and make it so that I will never be abandoned again. I wanted a family so I created one."

Reborn briefly closed his eyes, hating the fact that he understood. He understood all too well this feeling. He had craved for a family too, a long time ago, before he decided that he was better off alone.

(Reborn had noticed four years ago that the Guardians were suffering from Flame Addiction. He hadn't done anything to prevent it. That way, he knew that Tsuna would keep his Elements. Sure, as soon as the cravings started, their moods would turn for the worse, exacerbating their violent behavior from the simplest urge to snap at another one to brutally murder anyone who got in their way. Even so, he wasn't worried. Ferociously loyal Elements ready to bring hell on Earth were better than mellow and good-natured ones, in his opinion.

Of course, he had thought that Tsuna was still the sweet young man that could do no evil. To protect a Tsuna like that, he wouldn't need protecting dogs but rather, possessive beasts.

He wasn't the only one who believed it. Shamal had recognized the signs but hadn't done anything either. He was too fond of the Decimo to force a separation or something to prevent the Addiction.

By the time Ryouhei recognized the Addiction, it was already too late.)

"Because I'm greedy." Tsuna carried on, slowly stepping around his desk to approach. "I watched as more people came to me. I gained brothers and sisters in Fuuta, Lambo and I-pin. I found true friends in my Guardians and the girls. I met uncles and a grandfather that I had forgotten about. Suddenly, I had a family."

He stopped just in front of Reborn who was desperately ignoring how his Flames were settling in purring contentment under his skin as the Sky Flames enveloped them in a warm cocoon. From the explanation, Reborn retained two things. One, Tsuna was a natural in manipulation who polished his skill throughout childhood and learnt very well everything the hitman had taught him in this field to further perfection it. Two, while being extremely manipulative, Tsuna still had a pure heart. He was, fundamentally, a good person who would rather sacrifice himself than lose someone he cherished. He had flaws, obviously, with his selfishness the most noticeable, but he wasn't a monster.

Not like Reborn.

"You're all important to me so…I took precautions to never watch you leave." Tsuna finished as he came to a halt a few steps away from the hitman.

Reborn kept his eyes locked with Tsuna's, petrifying him on the spot as he prowled closer. His restraints were snapping at each step taken. He ceased to listen to his rational mind, letting his unacknowledged darkest instincts take over, strengthened with the craving burning in his veins through his Flames.

"Purposefully creating Flames Addiction wasn't very wise, Tsuna." He whispered huskily, eyes hungrily noting the shivers that ran down the Sky's spine at that. "Your friends yearn for the Harmony and calm you carry with you."

Tsuna wasn't even aware that he was taking a step back each time Reborn took one forward. He was completely focused on the hitman, ignoring everything else.

"And you're not?" He asked, picking up the hint.

"No, I desire much more than that." Reborn practically purred, vaguely realizing that he should stop before he went too far and possibly destroyed what they had. Damn it, he didn't want to. It had been too long that he had been repressing everything. "Cravings take multiple forms, including one that should never be incited."

Tsuna started when he felt his back touch the wall next to the opened window. An agreeable breeze ruffled his locks but he didn't move. He didn't dare to look away. He tilted his head up when Reborn successfully trapped him against the flat surface to not break the eye-contact. His breathing had slightly picked up, his heartbeat accelerating.

"As yours?" He questioned softly.

Reborn smirked. "Precisely."

With the last ounce of his control, he pulled back enough and let his hands fell at his sides, ignoring the urge to cage the other. He wanted to look away from Tsuna's slowly rising blush, dilated pupils and tongue wetting his lips. He couldn't, transfixed on the temptation that was the young Sky in front of him. He only had to stretch his arm to grasp Tsuna's neck and –

He broke his train of thought with a hitch in his breath as he stared at the slowly reaching smaller hand that was steadily approaching his cheek.

"Choose wisely, Tsuna." Reborn warned him in a low voice.

The hand paused in mid-air.

"What would happen if I step away?" Tsuna asked, eyes observing his features attentively.

"You have ensnared my Flames." Reborn admitted bluntly. "To keep things as they are, I will distance myself from you, close enough to settle my Flames but far enough to – "be in control " – stay focused."

"That's not what you want."

"What I want, Tsuna, is everything." Reborn couldn't help but get closer, invading Tsuna's personal space but without entering in contact with his hand. "What you can give, I'll take. What you can't, I'll snatch. Your mind, your soul, your body, your Flames… Everything will be mine."

Tsuna visibly shuddered at that. An odd expression crossed his features, too fast and complexed to be understood. There wasn't the slightest hesitation as Tsuna took the half-step necessary to also crowd into Reborn's space. His hand hovered near the hitman's cheek, the slight move creating a movement of air that disturbed his curl.

"There's no turning back." Reborn gave him a last warning, a last chance to back off before his inner beast snapped all seals and lunged avidly.

"No turning back." Tsuna agreed breathlessly.

His fingers caressed his cheek, skin finally meeting skin, Flames merging together in delight, and breaths released simultaneously with a shiver. Reborn's dark eyes met honey-colored ones and his restraints vanished instantly, freeing feelings and desires that he had sealed away for years.

His hands sneaked around Tsuna's waist and neck as he pinned him against the wall, tilting his head to crash their lips together and dominating the kiss in mere seconds, devoured the sweet temptation that was an aroused Tsuna in his arms. As Reborn delivered kisses on his neck before biting down decisively, he felt his Sun Flames flare in maniacal glee at a gasping Tsuna, twisting Flames betraying his pleasure, and smirked in triumph.

The Sky might have ensnared him with Harmony and peace, the Sun had succumbed to its charms only as it gave itself over as a willing offering to its impossible heat.

Reborn would suffer cravings every time he was away, but as he pulled back to gaze predatorily at Tsuna, he felt that out of the two, he was the one the least losing.

After all, once Reborn marked something or someone as his, no escape was possible.

A/N: Well, next one shouldn't be as weird or creepy as this one (though no one can be sure with how ideas evolve sometimes).

Flame Addiction: Elements, from a Sky to a Cloud, can develop addiction towards the Harmony released by a powerful Sky. It requires constant presence of said Harmony, a high familiarity to it and an attraction, linked to Flames, emotional or sexual, to plant its roots. The longer the Sky indulges with its attribute, the more frequent the Elements is under its influenced (acknowledged or unacknowledged), the easiest the Addiction settles. It takes from several weeks to several years according to the strength of the Sky and the stamina of the Elements. Once addicted, the Elements developed cravings, for the Sky. Cravings provoke different reactions: high aggressiveness, high stress, recklessness, sensitivity, loneliness when the Elements are away for too long from the Sky. Once basking in the Harmony, they calm down instantly, clear their minds efficiently and sharpen it for a limited time, boost their energy and (ironically) improve the stability of the Bond (if there is one in the first place). It creates a dependency towards the Sky. It isn't unusual for an addicted Element to waste away after the death of its Sky.

The cravings appear differently for each Element, corresponding from both the Flames and the personality. A Rain falls into depression. A Storm explodes more often than not. A Cloud grows hostile against all of the other Elements. A Lightning strikes indifferently allies and enemies. A Mist seeks isolation. A Sun grows destructive instead of healing. As for a Sky, its own Harmony is discordant and affects its Bonded.

That's my headcannon for Flames Addiction. If I were to write about it, it would greatly revolve around this description, with or without modifications. In this case, it would be as an independent story.

Anyway, thanks for reading, don't hesitate to point out any mistake or ask a question!

See you next time~