Neither remembers how switching began, just that one day, Yagyuu was slouching and Niou was sitting straight as a poker. They may have done it for April Fool's. They may have been mocking each other, but the point is that over the course of a few years it stopped being an inside joke, a prank, and was elevated to the level of...something else. The difference began in their junior year of high school when they switched the switch--Niou pretended to be Yagyuu pretending to be Niou. They loved to laugh about it, afterwards, but that day, something changed.

They didn't notice.

---

Yagyuu chose their college, then engaged in a series of battles against Niou, who wanted to drop out and slum around for a few years. Or forever. He didn't care.

Yagyuu did, and since the thought of removing himself from Niou's definition of his own existence was not only distinctly uncomfortable, but also conjured up visions of Niou falling into a life of apathy and crime and eventually dying young because he provoked the wrong people, Yagyuu dragged Niou through applications, through college, through classes and finals and graduation, and at the end of it all, through job interviews--Niou didn't speak to him after that last imposition, simply disappeared for a month and half--the longest sulk he'd had thus far--but after those infinitely dull six weeks had passed, Yagyuu returned to his brand new apartment one evening after a long day at work and wondered how it was possible for Niou to make this much of a mess in the space of a few hours.

He straightened the shoes at the door, put Niou's suitcases in his own bedroom, threw away the empty pizza box off the coffee table, put the filthy clothes around the couch into the laundry pile, tugged a corner of Niou's blanket down to cover the skinny, bare white feet that stuck out over one arm of the couch, and tugged out of his mouth a strand of hair (grey with neglect) that Niou had been chewing on.

Yagyuu often thought that being friends with Niou, living with him, was rather like walking a tiger; he had to be sharp and alert to keep Niou in line, otherwise the tiger would struggle and maul and shoot away into the jungle and disappear forever and Yagyuu would never catch him again.

On the other hand, when they switched, Niou had no choice but to be the one holding the tiger back. It was just how things were, and when he was Yagyuu, he was Yagyuu, and that was what Yagyuu did. Yagyuu knew that when they were switched, it would never occur to Niou to run.

---

It changed again the day Niou gave up his dye. He colored it back to what he claimed was his natural, while Yagyuu leaned against the bathroom doorjamb and looked on. Niou didn't admit that it was almost exactly the same shade as Yagyuu's, but he did grin at his partner, say that silver was getting old, and wouldn't it be more convenient for the switch?

Yagyuu had to agree, but wondered aloud if Niou would be abandoning his hairgel next. Niou laughed and went to wash out the dye.

---

Know someone for years, spend all your time with them, live with them, eat breakfast with them--you'll pick up their bad habits, and they'll pick up yours. Yagyuu had to bite his tongue sometimes, cutting off an irritated, "Puri!" and Niou found himself adopting Yagyuu's speech patterns in return.

Niou sat up straighter, Yagyuu's posture relaxed. They noticed. They dismissed it, because wasn't force of habit a funny thing sometimes?

---

Yagyuu couldn't remember how many pairs of glasses he'd had in his life. Strangely, Niou could, and mentioned that this was the fourteenth pair he'd broken, compared to the eight that had been lost or stolen or misplaced. He mentioned that if Yagyuu wore his switch-contacts all the time, he wouldn't have any glasses to break when Niou inevitably provoked barfights.

Yagyuu had to admit it wasn't a bad idea.

---

Once, when Niou dragged him to a ridiculous movie--all immature humor of bad-taste and violence--Yagyuu found himself cackling aloud at something unexpectedly witty one of the characters had said.

Niou didn't notice--he was too busy laughing at it too--but Yagyuu was more surprised at the fact that he didn't mind relaxing like that in public anymore.

---

No one ever mistook them for twins--they didn't look that much alike, after all. Yagyuu was just a smidgen taller, and softer and thinner of feature, while Niou's remained distinctly pointy; the size and color of their eyes was different, and the shape of their hands.

Still, sometimes when Yagyuu was brushing his teeth with Niou, beside him, styling his hair, Yagyuu would wonder, Am I sure that's me?

He didn't let it bother him--by this time, it was a comfortingly solid feeling, that unsurety, even when the slide of Niou's mouth agaist his neck, the bite of his teeth into Yagyuu's lip was the same whether Niou was Niou or whether he was Yagyuu.

---

What's in a name?

Sometimes he forgot and called Niou "Yagyuu."

Sometimes Niou did the same.

---

Individuality is overrated when you always know what someone else is thinking as well as they themselves do.