A/N Okay, I came up with this because I needed SOME inspiration to write another fanfic, and I happened to watch the Cardcaptor Sakura episode where Li and Kero switch. Hence, this fanfiction. I will continue this one for about 5 chapters, or at least until I get (or someone gives me) an amazing idea that can put my mind to work. C'mon people, I don't care if it's cheesy, angsty, or just plain stupid, I need an idea!

I don't own Prince of Tennis.

Chapter 1

Yukimura smiled at the games going on. After all, it was amusing to see doubles pairs playing against their partners.

"Game, Yagyuu-senpai and Jackal-senpai. 5 games to 3!" Kirihara called out nervously, trying to ignore the two tennis players on the other side of the court who were glaring at him, having just lost another game.

"Really Marui, try to improve your teamwork. You won't always be playing with me." Jackal advised, giving Yagyuu a high five before heading back to his position at the baseline.

"I agree. Niou-kun, you need to be flexible to whoever your partner is, and not just me." Yagyuu added.

"I don't care! If I have to play with him, I'd rather play singles!" Marui objected, pointing at his smirking doubles partner. "Niou-kun, be serious. Marui is becoming annoyed." Yagyuu sighed, although not dropping his stoic expression.

Marui couldn't tell if he obliged, but hastily went to the net when he saw Niou toss the ball up to serve. A normal serve was returned with a laser, which Marui struggled to reach but ended up too late as the ball bounced and crashed against the fence before he noticed it. "Niou! That was yours!" Marui glared.

"It was, but you were already trying to return it. Besides, Yagyuu's playing for real so even if I had reached it, I wouldn't be able to return it." Niou stated. Marui gave an exasperated groan, and swallowed his gum in annoyance when their kouhai said "Jackal-senpai and Yagyuu-senpai win, 3 games to 6…"

Both doubles pairs walked up to the net to shake hands with their opponents. It was then that the misfortune started, if it hadn't already.

"Tarundoru! That was a terrible match!" Sanada glared. Yanagi placed a hand on his shoulder and calmly smiled at Yukimura. Yukimura, understanding, nodded in approval.

"While it may have been a poorly played match, I can assure you that after drinking this, your playing capabilities will increase exponentially. Imagine all the potential that could be yours." Yanagi started.

Kirihara blinked in confusion. So did most of the other regulars. Because, you know, they have to blink… Oh, nevermind.

"Meaning, Yukimura and I both advise Marui and Niou to drinking this juice made by my friend Sadaharu. It's full of nutrients, and with both guarantee it to be one of the best juices he has made so far." Yanagi finished, and held out two cups containing a bubbling, rainbow coloured liquid.

Marui gulped nervously. "Um, Buchou, you didn't actually say it was okay for us to drink this, right? I mean, it's… changing colours, and looks really toxic."

Yukimura gave the self-proclaimed tensai a smile. "I think it's perfectly safe. Besides, if it can enhance both of your playing abilities, it's great, right?", he reasoned. He waited while Yanagi handed Marui and Niou the cups. They stared at it for a while, before deciding to chance it. Besides, not everything Inui made was utterly disgusting and poisonous, right? …Right?...

Judging by the speed that Marui and Niou ran to the washrooms, the regulars could correctly decide to never, ever, drink anything made by Yanagi's friend. Ever.

Marui and Niou ran to the washrooms at such a speed that they put the cross-country runners to shame. Unfortunately, by the time they got there, they had already swallowed most of the drink. Surprisingly, it was tasteless. But Marui knew that Yanagi put things other than vegetables in the drink, if the vinegar and squishy things he tasted was anything to go by. So, when they reached the washroom, all they could really do was try to spit out anything left in their mouth and faint.

"Niou-senpai! Marui-senpai! Are you okay?"

Opening his eyes a little bit, he could see Kirihara looking at him with concerned eyes.

"No, I am certainly NOT okay, brat! I am going to freakin KILL Yanagi for making me drink that stuff, dammit!" he responded automatically. His eyebrows raised when their kouhai looked at him, hurt.

"Marui-senpai? Are you okay? Why did you call me a brat? I know the juice must have tasted bad, but I didn't think you would want to kill Yanagi-senpai…", Kirihara trailed off. Widening his eyes, he shot awake, surprised. Did Akaya just call him Marui? This was a joke, right?

"Huh? I didn't call you anything, Akaya! And I would never want to kill Yanagi! He's annoying, yes, but even I wouldn't go that far!" the voice behind him protested. Kirihara looked genuinely confused.

"But, Niou-senpai, you're always saying mean things about his potions! And, I was talking to Marui-senpai." Kirihara informed. "What do you mean, I am Marui." the voice continued.

"No you're not," Kirihara stated, "You're Niou-senpai."

"What do you mean, brat, I'm right over here." he snapped.

Kirihara stared, confused.

"Ok, what's going on?" he shouted, and raised himself from his sleeping position to see the other two who were also in the room. This action was probably the smartest for him, but the others might have preferred to take their own sweet time to notice.

Marui yelled. "There's two of me!" he said, pointing at the "Marui" who had just stood up. Niou looked just as confused. "No, there's two of me. You've got white hair."

"What? Could it be that… that Niou-senpai and Marui-senpai have switched bodies?" Kirihara asked curiously. Hey, he was only a kid. These things didn't happen often.

The two looked at the mirror.

The scream could be heard throughout the school and even reached the tennis courts and soccer fields.