The moment Yamamoto heard that Giannini had abandoned mechanics and weapons in favour of making serums; he was positive that something was going to go terribly wrong. It was bad enough that despite the man's kindness, he was horrible at working with metals and solids, but to think that he would be working with liquids instead was enough to cause an uproar throughout the Vongola household.

In fact, Yamamoto wasn't sure how it had all begun in the first place, though something in the back of his mind told him that Gokudera's shrinking incident must have pushed Giannini past his limits. Days later, the man had made a frantic phone call to Tsuna, clearly stating his new intentions, and well... the rest was history.

Now leaning against Hibari's doorframe and staring at the exotic scene in front of him, Yamamoto wondered if it was best to run away and yell at Giannini for having ever given up, or thank him and gawk at the sight in front of him.

"Uh... Hibari? Is that... is that a tail?"

A hiss provided all the answer that he needed, though the swordsman couldn't take the ruthless teenager's fury seriously when he saw both a tail moving back and forth in irritation and an adorable set of cat ears on top of his head twitch. In total contrast with Hibari's personality, it was absolutely lovely.

Walking in cautiously, Yamamoto eyed the bottle that was lying innocently on the side of Hibari's bed. Instantly he knew that the teenager had fallen victim to one of Giannini's serums.

"Listen, Hibari," Yamamoto started, his lips turned upwards in a smile. "If you want, I could tell Tsuna that you're not feeling well? It's rare for you to take days off anyway, so I'm sure he won't-- oof!"

Falling to the ground with a grunt, Yamamoto eyed Hibari's narrowed eyes with a look of amusement. Apparently, being forced to stay in his room due to his new physical appearance did not make Hibari happy. Leaning back on his elbows, the Rain Guardian let out a sheepish chuckle before reluctantly pushing the neko off of him. He got up, walked over to Hibari's bed, and picked up the bottle.

Eyeing it uneasily, he began to read it. He was curious as to what it would do, and as to why Hibari would take such a thing in the first place. Neko in a bottle. Includes ears, tail, and purring. Warning, May cause unexpected and constant arousal, unusual lubrication, and deep sexual frustration. Stricken with shock, Yamamoto slowly turned to look at the dishevelled mess that was the neko Hibari.

"Why would you take something like this?" He asked. A playful grin began to spread across his face. "Did you take this for me? Did you want to see how far you could push my resolve before I snapped?"

"Stop acting like an idiot!" shouted Hibari. "If you must know, the baby insisted on my cooperation to try out that fool's serum."

"And what about the side effects?" Yamamoto snickered. "Did you skip over those on purpose?"

"Sh-Shut up! I'll bite you to death, you assho--"

"Or maybe," Yamamoto cut him off as he walked toward the door, a devious smirk on his face. "You were hoping that I'd push you past your sexual limits, forcing you to submit to me as I plunged deep inside of you?"

Walking outside, Yamamoto barely missed the bottle that was thrown at him as he shut the door behind him with a grin. I'll give his body and his mind some time to crave my touch. Then, perhaps, the fun will begin.

------------------------------------------------------------------------------------------------

Not sure what he would see upon his arrival, Yamamoto open the door slowly. To his delight, he found the Cloud Guardian sprawled on his back with his cheeks flushed in arousal as his hand worked at a heavy erection between a set of pale, toned thighs.

Feeling his gut tighten in lust, Yamamoto watched as Hibari squirmed, his body tense and his eyes sharp as he stroked his rigid cock quickly. Despite the rough treatment, his head was tilted back in pleasure. Yamamoto couldn't help but move closer in interest.

As his eyes rolled over Hibari's figure, he noticed that the subtle mews that the neko was exuding were becoming louder as his jerking hand stopped at his cock's leaking head, twisting it lightly before moving back down to its pulsing base. Yamamoto's hand twitched as he realized that Hibari's orgasm was approaching. It yearned to be the one stroking the lovely length that drooled copious amounts of pre-cum. He longed to feverishly lick the tip, to lap at it hungrily as the fierce teenager cried out his name.

"F-F*ck!"

The Rain Guardian watched through half-lidded eyes from the middle of the room as Hibari's back arched erotically, his hand milking his orgasm for all it was worth as heavy amounts of cum landed hotly on his abdomen. Watching the arcs of sperm land on his body, Yamamoto smirked at the boy. Letting his eyes take in the sight of the lethal teenager covered in his own juices, he couldn't help but notice that his erection hadn't subsided after his orgasm. In fact, it looked harder and even larger than it had before. The skin around his cock was more taught, causing his veins to look considerably larger and more pronounced as blood surged through them. His new, achingly large looking cock pulsed with need and desire, a desire for the hot touch of another. Yamamoto stared in awe at Hibari's glistening midsection. His throbbing length was practically demanding to be soothed by his own, still twitching hand. Not wanting to disappoint the teenager's aching length, nor his own lustful desires, the Rain Guardian slowly sauntered toward the sinful sight that was the neko Hibari's body.

Keeping as quiet as possible, Yamamoto kneeled before the Cloud Guardian and delicately placed his hand around his length as he slowly cleaned off the juices from the hard cock with his tongue, chuckling as he heard Hibari shout in protest.

"L-Leave now, herbivore, or I will bite you to death— ah!"

Tracing the throbbing vein roughly with his thumb, Yamamoto grinned before moving upward to the sensitive triangle of skin just below the purple head. "Actually Hibari," he muttered while eyeing the teenager's lascivious cock with desire. "You are in no position to bite me." To prove his point, Yamamoto grazed the underside of Hibari's erection with his teeth, all the while enjoying the lustful and provocative sounds escaping the teenager's mouth. As he pressed an open-mouth kiss on the sensitive triangle, he flicked it with his tongue and began to suck at it ruthlessly, all the while enjoying the salacious cries he received in return.

"Nnn! F*ckin' idiot. S'good..."

Hibari looked as though he was losing his mind, which was exactly how Yamamoto wanted him to feel. He wanted the boy to be breathless, out of his mind and crying for more. He wanted to tear apart Hibari's cold shield and replace it with something burning and passionate.

Chuckling at his thoughts, for they were serious in comparison to his normal attitude, he licked at the frenulum a few more times, lavishing in the sounds of pleasure that he received while doing so. Sensually, he kissed his way up to the swollen head of Hibari's cock. Pulling back to admire the sinfully delicious sight that was the Cloud Guardian's erection, Yamamoto noticed that his cock was teeming with pre-cum as a large pearl of it leaked subtly out of the pink tip.

"So Hibari, you're aroused because of me, ne?" He started to laugh, a sheepish grin on his face before realizing that the fierce teenager underneath of him was glaring in anger. In apology, he bent forward and stuck his tongue lightly inside of Hibari's urethra, receiving a small taste of pre-cum as it erupted from the head. Content to hear that he was clearly forgiven, due to a tug of his hair and a groan of longing that signalled Hibari's desire for more, he closed his eyes as he took in the taste that was uniquely Hibari's. Knowing now to keep his mouth shut, he ran his tongue across the top of the wet head in continuous strokes, watching as it glistened with his saliva. His hand, having practically stayed at his side this whole time, finally eased its own desires as his fingers began to stroke the tight set of balls just before cupping the sacks and rolling them around gently while he engulfed Hibari's length deep into his mouth.

It felt surreal, so goddamn hot and he could not get enough of it. Hollowing his cheeks as he bobbed his head, Yamamoto felt his own cock twitch and leak as an aggressive hand pulled at his hair, and groans of an unquenchable sexual thirst tantalizing danced through his ears. As the Rain Guardian's hand on Hibari's balls tightened from the erotic and needy sounds of his fiery lover, an undignified sound erupted from the depths of the teenager's throat. The normally controlled teen had snapped causing his hips to thrust violently against the hot mouth.

Allowing Hibari to have control of the situation momentarily, he pulled his hand away from the drawn-up balls, and instead wrapped it around Hibari's twitching tail, stroking it in time with the thrust of the teenagers' hips.

"D-Damn ba-ka.."

Looking up at the Cloud Guardian, the question in Yamamotos' eyes was enough to surprise Hibari. It was clear from the carnal look in the baseball players' eyes that he wanted nothing more than to give pleasure to the fiery boy.

Does it feel good?

"Hn. You're s-sufficient, herbivore."

Smirking at Hibari's reply, Yamamoto pushed himself away and ignored completely the line of swear words that were directed towards him.

Moving further down the bed, the Rain Guardian pushed Hibaris' knees up towards his chest, revealing two luscious, pale cheeks. "I refuse to be sufficient Hibari, because I intend to make you need me, to want me with every ounce of your sexual desire. No one else could give you this pleasure," he whispered huskily, enjoying the slightest hint of pink that adorned his soon-to-be lover's cheeks. "No one else possesses the power to make you submit. I'm the only one who can make you feel these things; don't forget it Hibari."

Taking the teenager's virgin cheeks in his large hands and spreading them, Yamamoto was surprised to see the pink entrance twitching and wet. Strangely, it seemed that it was self-lubricating, most likely a result of the serum, yet he was aroused beyond belief at the sight of Hibari's enticingly dripping hole. The thought of how easy it would be to prepare him and slide deep into that hot heat made Yamamoto groan in anticipation. How convenient.

Leaning forward, a devious smirk etched on his face, Yamamoto stuck out his tongue and traced the teenager's puckered hole with the tip. A reluctant groan from above encouraged him to put more pressure on the sensitive skin.

"Y-You f*cking asshole! Th-That's filthy. Stop it!"

"Actually, Hibari," Yamamoto whispered in a sultry voice, his tongue probing at the teenager's wet entrance before pulling away. "Your asshole keeps twitching wantonly for more. It's wet and practically gushing with an erotic lubrication." Yamamoto grasped Hibari's cheek with his large, masculine hands and used his long fingers to spread the cheeks far apart before plunging his moist tongue inside of the lubricated hole, grinning as he heard a series of moans that escaped Hibari's lips.

Making sure to tease the Cloud Guardian, Yamamoto eased his tongue out gently and licked in long strokes at the pink hole that seemed to twitch in an unfulfilled desire. The lubrication that was drooling from Hibari's puckered hole was warmly sliding down his throat and collecting in the pit of his stomach where it was beginning to burn. It was making him feel feverish and sweaty. His eyes were beginning to glaze and his cock was sweltering with an intense desire to be consumed and embraced by the intensely erotic hole. He wanted to soothe his massive and searing erection, to bury his heavily leaking cock deep in Hibari's feverishly moist entrance. He needed more though; he needed to taste more of the exotic and strangely seductive lubrication that was spilling from the Cloud Guardian's pink hole. He buried his face deep between the teenager's cheeks and lapped eagerly at the twitching, leaking entrance. He re-inserted his tongue into the delicious hole, watching with half-lidded eyes as Hibari spread his legs, begging earnestly for more.

Licking his lips as he wiped a trickle of drool from the corner of his mouth, he looked up. "Do you enjoy being filthy?" he taunted as he circled Hibari's entrance thoroughly, his tongue roughly coating the hole with saliva. Yamamoto watched the puckered skin twitch for something to fill it, instantly feeling sparks of arousal uncoil in his gut. His cock was already achingly massive from the aphrodisiac of Hibari's hole, but he knew that he would have to thoroughly stretch the ruthless teenager's tight entrance before thrusting his heavy cock deep inside. The sheer thought of being able to calm his fiercely raging erection in the Cloud Guardians perfectly tight heat caused his cock to drool lavish amounts of pre-cum.

Pulling back reluctantly, Yamamoto moved one of his hands away from Hibari's supple cheek and slipped a finger inside, nearly cumming at the feeling of pressure the Cloud Guardian's hot walls were exuding. It was so tight and he wasn't sure how he would f*ck Hibari without coming instantly. Shaking the thought away, he inserted another finger, pleased to hear more cries of pleasure escaping his Hibari's lips.

"F-Fucking herbivore. M-More, damnit!"

Yamamoto wasn't surprised that Hibari was going to be a needy uke. In fact, the thought caused him to grin proudly, and if he had anything to say about it, he was going to make him scream, scream his name loudly and with a longing desire.

Thrusting a third finger inside, he began a quick and awkward pace as he tried different methods in an attempt to please his uke. Twisting his fingers and curling them upward, he was shocked to hear a breathless groan from above.

"Are you alright Hibari?" Looking up with ignorant concern, his eyes widened in surprise as he saw Hibari's narrowed eyes, parted lips and several rough thrusts against his breaching fingers.

"D-Damnit, I will bite you to death if you do not f*ck me!"

Laughing at Hibari's urgency, he curled his fingers to touch at the teenager's prostate one last time before pulling back his hands to tug at his boxers and release his own engorged, heavily leaking cock. Watching dark, gleaming eyes widen with hunger and shock, he knelt in front of the parted legs, pride radiating from him; he couldn't wait to make Hibari lose control.

Smirking, Yamamoto turned the Cloud Guardian onto his hands and knees, ignoring the curses that left Hibari's sinful lips as he jerked his thick length lazily for a few seconds before pressing it between the supple cheeks.

"I hope you're ready Hibari," he whispered hotly into his ear, his aching cock rubbing against the wet hole. "Because I'm about to make you scream, scream like the submissive uke that you were meant to be."

Ignoring the angry retort, he lined the head of his cock to Hibari's tight, drooling entrance before thrusting his hips forward. His cock suddenly became enveloped in hot, wet heat. It was an excruciating feeling, so tight and hot, oh-so taboo yet astonishingly addictive. The feeling of Hibari's velvet walls massaging his length would have made Yamamoto cum had he kept thrusting. Instead, he controlled his breathing and waited patiently for his throbbing cock to subside.

"Y- you stupid idiot! Why the hell did you stop?!"

Leaning forward, Yamamoto whispered, "I'm pretty sure that you wouldn't appreciate me cumming before you, right?"

Eyes wide, Hibari turned his head to the side as a subtle blush covered his cheeks.

"Hurry the f*ck up then."

Nodding his head, Yamamoto shut his eyes and gave a small thrust to test his resolve, content that he didn't feel like shooting his load right away. Picking up his speed, Yamamoto grabbed Hibaris' hips roughly just before losing himself to the pleasure. His thrusts were deep and rough, his large cock spreading the Cloud Guardian's entrance wide as the head of his erection collided lustfully against Hibari's prostate.

"A-Ah! Sh-Sh*t!"

Mouth open, hips thrusting with all of his might, Yamamoto took in the erotic and sultry sounds around him: Hibari's panting and widely choked moans, the sound of his balls slapping against Hibari's tense behind, his own passionate groans. It was so wrong that it felt right. Being friends with Tsuna had shot him into a whirlwind of intensity; this raw and carnal sex with Hibari was only another addition to the complex equation of his changed life and he wouldn't stop for anyone.

"Y- you're so tight Hibari... gripping me so tight-ly..."

Grinding his thick cock deep inside of Hibari's body, he reluctantly let go of one of the teenager's hips so that he could wrap his large hand around the needy, drooling, heavy cock. Panting intensely into the Cloud Guardian's ear, he jerked at the immensely wet and brimming erection roughly, trying to get Hibari off so that he could succumb to his own brewing orgasm.

Hearing familiar cat-like mews coming from Hibari's pink mouth, Yamamoto wasn't surprised when the Cloud Guardian jerked forward with a choked scream of his name, his cock twitching as loads of cum coated his chest and Yamamoto's hand. It was too hot, too surreal; the feeling of Hibaris' walls tighten on his own erection, urging and pleading his orgasm out of him. Yamamoto thrust awkwardly into the wet entrance a few more times before letting out a loud groan, his cum shooting out and covering Hibaris' walls with his seed.

Falling forward, Yamamoto tried to control his erratic breathing as his dry hand moved to the top of Hibari's head were it massaged gently at the cat ears that adorned the black locks of hair. Smiling, Yamamoto cherished the moment of silence, save for the low sound of purring, for he knew that once Hibari woke up from the afterglow, he'd be bitten to death.

...Yet for once, he didn't seem to mind. It wasn't because love or affection were situated in the room. No, it was simply the feeling of utter serenity that urged him to relax and enjoy the moment.