Rin could only remember being sick once in his life. And chicken pox didn't count, if he was thinking in terms of the common cold.

Yukio only got sick occasionally when they were younger-not as frequent as expected from most people. Especially the ones who'd heard the stories about him being a smaller kid, quick to cry and easy to pick on.

But Rin? He didn't get sick. It was the whole half-demon thing, because there was no way the human side would've been able to avoid the flu that had spread like wildfire through True Cross Academy a few months back.

And at that moment, in the few seconds it took for him to cough, he: a). thought Was that me? b). briefly wondered if he'd swallowed his own spit wrong and c). felt the heavy weight of the cram school students' gazes drilling into his back.

He opened his mouth to address the staring-and sneezed.

Twice.

Yukio paused in writing on the blackboard long enough to glance back at him, eyes narrowed. "Rin?"

Rin cleared his throat. "M'fine."

Fifteen minutes later, the coughing got worse.

Shiemi held a hand hesitantly close to his shoulder, as if she were going to pat him on the back. "Are you sure you're okay, Rin? You aren't sick, are you?"

"I don't get"-cough-"sick."

The look on her face told him that she thought he was full of it.

"Tsh. Moron can't even admit when he's sick." From Suguruo, naturally, flipping through the demon pharmacology book. Rin felt sapped-he didn't even have the energy to tell the rooster-head off, like he usually would.

(This in itself should have alarmed everyone.)

When Yukio turned to Rin a second time, the pleasant-teacher mask he wore slipped for a moment.

"Rin, do you need to go to the infirmary?"

"No-" his voice came out rough, and his throat burned when he tried to swallow. "No, I must've just had my face to close to these dusty ass books and breathed something in."

Yukio gave him the same look that Shiemi had, albeit with more annoyance and the familiar Rin-don't-screw-around undertone.

Five minutes later, Rin closed his eyes for no less than a second before he pitched sideways out of his chair.

(Later, he would reflect on how disappointing gravity had been to send him into the aisle and not, say, to the other side, and into Shiemi's lap.)

"Oh, ho, ho! Seeping beauty awakes!"

Rin cracked his eyes open to hot pink pokadots and a goatee that was painfully close to his face.

"Fu-M'phisto, get outta m'face."

Yukio was anxiously standing on the opposite side of Mephisto. "How are you feeling?"

Rin self-assessed.

Arms, fine. Legs, fine. Neck, a little stiff. Head, pounding, dear God, what demon had stuck an ice pick in his eye? Throat...he swallowed once and resisted the urge to claw his neck. His chest was sore, and his sternum felt like a boulder was nestled atop it. Breathing was terrible-the wet, rattling in his lungs put his nerves on edge.

Was this what it felt like to be sick?

"I take it that you won't have a positive answer for us," Mephisto chirped. "Doesn't surprise me, either. A little itty demon has made its way into your immune system, Rin! Usually, the snots like the one you've got in you wouldn't bother with a higher demon because they'd be killed before they could do any damage, but it seems that yours is a little extra special."

Rin closed his eyes and almost whined. He didn't want to try to solve any riddles at the moment.

"Extra special as in someone engineered this demon," Yukio clarified. Ah, helpful Yukio. Rin squinted at his brother.

"Huh?"

"We've run some blood tests, and it looks like whoever made this bacteria made sure it would have enough demonic presence to get you sick. It's not strong enough to kill you or anything, but you might feel like hell for a couple of days."

Rin tried to groan, but it came out as a breathy hiccup. "So you're saying someone is doing this on purpose."

"Unfortunately," Mephisto winked at him. Rin pretended not to see it. "But on the bright side, this means someone at the Acaaa-de-my is up to something." He sung the last part as he straightened his coat and gathered his hat under an arm. "I'll be off now, boys! Rin, get plenty of rest, eat soup. Yukio, carry on with your normal duties."

And he swept out of the room.

Yukio's eyes stayed on the door after he'd gone, frowning. "I hope he realizes that I'm going to have to skip cram school to look after you."

"Aw, are you going to make me soup?"

"No, I'm going to sit and laugh at your misery in return for all the years I got sick and you didn't."

Rin couldn't tell if he was serious.