A/N:

Hails: I blame Tumblr, I'm too susceptible to influences and writing prompts. The one I saw was too good to pass up. LoosingLetters decided to write the angst one and then Faisalliot said something that was so spit-my-water-out hilarious about Rin and Yukio that I absolutely had to write it.

Prompt: You live in an alternate world where twins - fraternal and identical - can feel each other's physical pain. You are an only child with no siblings. One day, suddenly, you feel a burning pain in your chest.

Faisalliot's Prompt: "Could you imagine Rin and Yukio, though? Like, they sitting in cram school and Yukio is teaching the most boring lesson possible and Rin suddenly gets an idea. Yukio doesn't trust that glint in his brother's eyes, not for a second, but he keeps teaching. [The rest is omitted]"

Rin yawned, leaning his head on the palm of his hand. Yukio was teaching a particularly boring lesson on the uses of plants that protected one's house (blackberries, ivy, rowan, and mistletoe.) Next to him and behind him, Rin could hear Shiemi and Izumo furiously scribbling down notes, and he didn't need to glance behind him to know that Suguro probably had five pages worth of notebook paper filled with the uses of one herb.

Thunk!

Rin felt a sudden shot of pain run through his knee.

"Son of a-" Both twins went into a quick, muffled cursing spree, both of them clutching their right knees. Rin knew instantly what had happened. Yukio had banged his knee against the table while teaching.

"Watch it," Rin whined with a pout. "That hurt."

"Sorry, Rin," Yukio said. He took a minute to sit down and wait for the pain to ebb away. "I didn't mean to."

"It's alright," Rin waved it off, putting his feet back on the ground. "Are you okay?"

"I'm fine," Yukio answered. "And you?"

"Yeah."

It was then that everyone simultaneously remembered that Rin and Yukio were fraternal twins and could feel each physical pain. A couple of them winced, an automatic feeling of pity washing over them.

It sucked to have a twin brother sometimes. Rin and Yukio had both thought that at some point, particularly when Rin would come home after a nasty street fight, skin broken with cuts, scrapes, and bruises; bloody knuckles and black eyes and chipped teeth. You should've seen the other guy, Rin would say with a goofy grin. It took Fujimoto a profound ability of patience and restraint not to smack Rin upside the head to prevent distractions in Yukio's presence. Yukio would admit it was frustrating to feel brisk stinging sensations against his knuckles, sometimes on his face or gut where Rin's opponent retaliated. It didn't help that disinfectant stung and made it difficult to get Rin properly treated for his afflictions.

Once the matter resolved itself, Yukio went back to teaching his lesson on blackberry wreaths, and Rin burrowed back into his thoughts.

A sudden bulb flicked on like a light. A mischievous, devilish smile worked Rin's lips up as the little imp known as his Id crept up his shoulder and giggled roguishly. Yukio felt a chill run up his spine and he whipped around to meet Rin's sparkling gaze, the older of them who happened to be interested in the lesson—that which never happened.

"Don't," Yukio warned.

"Don't what?" Rin asked innocently.

"Don't do what I know you're about to do," Yukio said. He pointed an inch of white chalk in Rin's direction threateningly. "Don't even think about it. I can read your mind."

"That's creepy~," Said Rin dismissively. He was still smiling, however.

"Shut up and pay attention," Yukio snapped. He turned his back to his brother and continued writing down organized points of reference about ivy's cleansing properties.

Rin, however, had other things in mind. He waited a moment or so, hoping to sweet Jesus that Yukio would let his guard down just a tiny bit. It seemed fate rewarded the patient because Yukio fell back into his teaching routine rather quickly. Slowly, ever so slowly, Rin reached over to his side, his fingers ghosting over the fabric just on his ribcage. He pinched. Hard.

Yukio suddenly made a noise between a scream and yelp as he tripped, gracelessly falling to the linoleum floor in an undignified heap. He curled up in a ball, whimpering and trying to nurse his pained side. Rin, however, refused to keep a straight expression despite his poker face abilities. He repeatedly pounded his fist on the desk, howling with laughter. He, himself, toppled onto the floor ignobly. He could hardly contain himself, his sides and stomach aching from hard he was laughing. This, of course, causing Yukio some grief and the disability to stand and scold his brother. God, everything hurt so bad. His back from when Rin fell onto the floor, his side which Rin pinched, his stomach because dearest creature in creation, couldn't Rin learn to STOP LAUGHING.

"Rin..." Yukio wheezed through the pain. "You piece of shit, I hope the Vatican executes you."

Rin giggled at the response. "Go kick a brick, four-eyes! That was funny and you know it."

"But you're not the one who's in pain!"

"Both of you knock it off!" Ryūji's chair screeched as he stood abruptly. He pointed at Rin accusingly. "Rin, get your ass back in that chair before I put you back in it! Mr. Okumura, continue the damn lesson before I pull my hair out! This is supposed to be a respectable school, you morons!"

Both twins managed to gather themselves together. However, Yukio continued sending Rin furious black looks the entire lesson, almost daring him to try that stunt again. But it seemed Rin decided he was going to behave, and either way, Yukio knew what type his personality was. He didn't get angry, he got even. His fingers brushed over the back of his neck thoughtfully.

Rin has a sensitive nape, right?