DISCLAIMER: Akira Amano is the genius behind the characters and the concept of Katekyoshi Hitman Reborn. I don't own them.

Pairing: 1827 [Hibari x Tsuna]

Contains: Light BL (Boy's Love), Kissing and the greatness of Reborn.

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Doki-Doki Syndrome

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Doki-Doki

- [v] Is onomatopoeia used for the supposed sounds of heartbeat while you are in the presence of the person you like. It is usually seen used in the Japanese subculture of anime and manga, especially in the genre of shojo.

Doki. Doki. Doki.

That herbivore was loitering on the corridor again.

The prefect scowled as he saw that group of herbivores crowding in the hallway again. He rubbed his chest brusquely when his heart started to thump a little too loudly for his taste against his ribcage, making the annoying sound again. He was sorely tempted in sticking his tonfa against the lump of tissues to stop it from going 'doki-doki' on him—that was his normal way of dealing with things, people and places that annoy him—but seeing as to that it was his own part that was causing the irritation, he didn't have much say in the matter. There was always the option of the expensive transplant but there were also the downside of long wait and hassles of dealing with people

Doki. Dokidoki. Dokidokidoki.

"H-hibari-san!" The startled voice made his heart perform cartwheels to the extreme; Hibari made a mental note of 'talking' to that guy who spreads the infectious 'to the extreme!'

"We weren't doing anything suspicious, wrong or illegal, I swear!" Brown eyes stared at him pleadingly while its owner managed to get behind his taller companions without breaking eye contact. "P-please don't bite me to indecipherable, tiny pieces."

He felt a prickling sensation in the left part of his chest, making him wonder if his box weapon got out without any activation. His jacket swished as tonfas were retrieved from some four-dimensional packet of air and he posed to attack. The baseball player and dynamite-wielder retaliated by bringing their own weapons out, preparing themselves for the attack, protecting the person using them as human shields.

Doki. Dokidoki. Dokidokidoki. Dokidokidokidoki.

He thought he saw something green on the corners of his sight; his hands were cold and sweaty, his throat dry and the disturbing urge to do something other than biting Sawada was overwhelming. He was certain that his heart was going to jump out of his body with the intensity of the 'doki-doki' sounds he could hear ringing in his ears.

There was definitely something wrong with him.

He hid his deadly weapons back to the dimensional packet and walked pass by the three students, ignoring the disbelieving looks on their faces. He won't let the poor condition of his health hinder his responsibilities as the head of the disciplinary committee—even if he had to admit that he was susceptible to the frailties of the average human.

So, we all reach the conclusion that Hibari Kyouya, the fearsome and not-so-invincible head of the Namimori Disciplinary Committee was sick (and that he had a trace of humanity somewhere in his body.)

A visit to the school infirmary was in order.

.x.

Reborn, who was currently engaged in his quality cosplaying time, was sitting comfortably at the large leather swivel chair dressed in a doctor's lab coat accented with stethoscope and eyeglasses. He smirked as the door slid open and waited patiently until it was closed again.

"Ciaossu," The Arcobaleno greeted, lacing his fingers expectantly. "Hibari Kyouya, what could the doctor do for you today?"

"Infant. Where's the doctor assigned here?"

"Shamal's asked me to sit-in for today. My medical degree and doctoral degree in unheard illnesses were getting rusty so I accepted. Please take a seat," Reborn explained. He didn't feel like mentioning that he kicked Shamal out of the window and distracted him from going back by letting him chase Bianchi dressed in a revealing sailor's outfit. Playing doctor was not the same without an office after all.

Hibari listed their school doctor's name on the back of his mind to get a 'visit' from the Disciplinary Committee.

"My heart beats in a very irregular pattern; it suddenly speeds up and makes these 'doki-doki' sounds."

"Hmmm." The small doctor rubbed his chin thoughtfully."When did this start?"

"Exactly two months ago."

"After you returned from the future?" A nod. Reborn tapped his blinking green pen on the wooden cardboard he was holding. "It just might be arrhythmia due to stress."

"Stress are for herbivores." Hibari snorted.

"Are there any other symptoms aside from the distinctive doki-doki?"

Hibari frowned, his forehead creasing as he tried to remember other signs associated with his current condition. "My hands sweat profusely, my stomach impossibly flips and I feel lightheaded sometimes. And I feel really confused, especially when around Sawada Tsunayoshi."

Sounds of scratching occurred as Reborn started writing the details down. He kept nodding here and there, pausing and resuming writing again. After five minutes, he stopped, put the pen and board on the table, and looked at his patient.

"The symptoms fit that of the doki-doki syndrome."

"Aren't you going to do the standard procedures of examining a patient?"

"Don't be ridiculous; a great hitman only needs his eyes in order for him to draw a correct analysis." Reborn scoffed at the young man. "Continuing, this syndrome is not exactly a form of illness but more of a condition that normally occurs in humans and non-humans like you, especially when you are around the source. Its harmless but unprecedented results will happen if you continually ignore it."

He jumped out of his seat and motioned Hibari to follow him. The prefect didn't budge and simply stared at the infant.

"Well, don't you want to find the cure for it? I'm sure you'll be very interested." Reborn smirked, the glint on his eyes foreboding.

Hibari stood up and followed wordlessly.

"If left untreated, said condition causes irritation and great confusion, making the person lose his control," Reborn explained as they walked along the corridors of the Namimori Middle School. "And if the right cure is administered, feelings of possessiveness, nervousness and happiness when around the object of the syndrome occur."

"We are going to see the cure," Hibari stated, having the perfect idea of who was the source and the cure of his predicament.

"Very good; the source is always the cure."

Reborn expected nothing less from the sharp guardian; he did choose Hibari. They stopped in front of the door under that hanging sign '2-1' and Reborn opened it unceremoniously, without any regards for the ongoing class—this was a medical emergency. The teacher swallowed his protests when he saw the prefect standing behind the intruding baby.

"Your cure is waiting, Hibari. Good day."

The Arcobaleno left, humming in a very satisfied tone. All in a day's work.

.x.

Doki. Doki. Doki.

Fluffy brown hair, large hazel eyes and trembling, pouty lips were the first to greet his sight; itmade his heart an acrobat, climbing in the trapeze set up inside his chest. Of course, the source of his dilemma was that small, pathetic yet strong-willed, stubborn, adorable Sawada Tsunayoshi.

There was nothing wrong with Hibari after all.

.x.

Doki. Doki. Doki.

The door of the classroom suddenly opened and standing there was the head prefect.

The young Vongola put his right hand over where his heart was currently jumping madly up and down to some unheard rock song, trying but failing to calm the overexcited heart. He once complained to Yamamoto about it (since Gokudera would likely threaten the best cardiologist with his dynamites if Tsuna told him about it) and the baseball player assured him that it was normal since his own heart goes like that too when he sees Gokudera. But Yamamoto and Gokudera were friends, no matter how much the Italian denied it at every chance, so that was probably normal for the baseball player.

He didn't understand why he only feels like this when he sees the frightening leader of the disciplinary committee; Hibari and he were not friends, right? Sure, the prefect was his cloud guardian but that didn't mean much right? He frowned when his chest felt a little bit tight.

Doki. Dokidoki. Dokidokidoki.

The blue-grey eyes stared intensely. He could feel Hibari's gaze penetrating very deeply into him; his cheeks felt warm. "Sawada Tsunayoshi."

Doki. Dokidoki. Dokidokidoki. Dokidokidokidoki.

Hibari was coming closer, really closer. His heart was now participating in a very violent drag race with the sound of that voice. He really should stop big brother from dragging him into those extreme marathon. "Sawada Tsunayoshi. Meet me at the reception room after classes, alone." With that, Hibari stalked out of the room.

Sawada Tsunayoshi was definitely sick with some heart virus. His hands felt so clammy and butterflies were wrestling inside his stomach; aside from the bruises he would definitely get after the visit, he would discuss these weird symptoms with the doctor.

Maybe Reborn could help him with that. His tutor, after all, is the epitome of walking madness and strangeness.

.x.

The other boy had not made any move even after Tsuna took a step inside the room. He just kept on staring with his unreadable face at the small mafia boss, making Tsuna fidget in discomfort. He braced himself when Hibari finally stood up and took smooth strides toward him.

Hibari kept on moving forward until he had the younger boy backed into the wall. He laid his hands on both sides of the brunet's head, trapping him completely. He leaned closer, his eyes meeting the other's expressive eyes, their breaths mingling. He smirked when he saw that blush adorn Tsuna's cheeks.

Doki. Doki. Doki. Two hearts were now beating in sync.

"Tsunayoshi." Tsuna closed his eyes when the warmth of Hibari's voice caressed his right ear.

Dokidokidokidoki. Hibari licked the shell of the organ before biting lightly, delighting at the squeak he elicited from the smaller boy. He returned his attention to the other's face and then captured those trembling, slightly pouted lips.

Dokidokidokidokidoki. Tsuna gasped, letting Hibari's tongue enter his mouth. Hibari didn't waste any time moving, mapping the inside of the soft and wet cavern. He teased the other boy's tongue, coaxing it to respond instead of remaining still. A tentative lick at first, then Tsuna moved against the older boy, copying him clumsily. He liked how Hibari tasted...

Big, warm hands settled on the small of his back and pulled him closer, molding Tsuna against the hard, solid body in front. Tsuna's hands were now wrapped around the taller boy's neck for support; his legs would give out with the mix of emotions he was in right now. He stood on his tiptoes for more leverage, and then deepened the kiss, tongues now engaged in primeval battle of dominance. Hibari bit his lower lip a tad too hard and once again took control.

He broke the kiss when he felt that his lungs would give out due to lack of oxygen. Hibari could not resist giving the flustered brunet one final lick on his swollen lips, earning a pretty flush.

Doki. Doki. Doki. Both of their hearts were still dancing cha-cha to the extreme but they didn't mind. It was not as annoying or worrying as before—it was kind of comforting to hear the two sounds they were making.

"From now on, I will kiss you so I won't have to deal with that annoying 'doki-doki'."

Tsuna let out a small laugh and didn't protest when he was swooped for another round of kissing. This was a lot better than swallowing pills and having injections.

Hibari thought that this was probably the best medicine invented.

.x.

"So, what was wrong with that violent student?" Shamal inhaled the addictive smoke before releasing it with a puff. "Is he dying?"

"Don't worry," Reborn threw the wooden cardboard at the man's table before removing his coat. "It's not anything that Tsuna could not cure. He is the Vongola Decimo so nothing should be impossible for him." He smirked before opening the locker of the infirmary room, disappearing into one of his countless hideouts inside the school.

Shamal looked at the item Reborn left. "What the hell is this 'doki-doki' syndrome? And is this...the young Vongola kissing that scary kid?"

.x.

Doki-Doki Syndrome is characterized by accelerated and irregular heartbeats; includes excessive sweating, increased temperature, and kinesthetically inclined organs (stomachs flipping, etc.). The said syndrome usually happens to everyone so it's not life threatening but if continuously ignored, it may result to very confused herbivores and highly-annoyed carnivores, which may result to misunderstandings and bloodshed.

Kisses are the only proven and tested treatment for this condition.

Upon the administering of the cure, heat flashes, groping and loss of clothes and virginity may happen. The certainty of limping is one hundred percent.

Doctor Reborn's Notes:

It's a normal condition, especially when you are around the person you like –even if you don't realize it due to being Dame-Tsuna or being a carnivore unfamiliar with the 'liking' territory.

Dr. Reborn's Advise:

Kisses. Lots of it. And please, do not forget to use lubrication when you reach the third base.

For personal consultations, please visit the greatest hitman/tutor/mathematician/doctor that graced the Earth, Reborn-sensei. Please watch out for possible mental and physical scarring and bullets when the doctor is in.

.le fin.

Jumping out of SasuNaru for a breathe. My first delve into the KHR fandom with my most favored pairing; and Tsuna, you're an uke no matter what they say *is shot*

Reviews are accepted :D