He would have his doubts that she really was L. He would have to test the waters no matter which way be believed. And the longer he sat on it, the more time she had to watch.
It would also provide an excellent opportunity to gather tangible evidence that he was Kira. He'd passed the round-the-clock-observation test with flying colors, but there was still something to him. Popular, yes; antisocial, perhaps. Antisociality, after all, was general disregard for the rights of others, for societal norms. To subscribe to all of society's norms to a T, down to the girlie mags, was more than a little grotesque. Every normal person has some sort of abnormal hobby. Abnormal people take normality to a whole other level. Bastardize it. On the other hand, Light was less aggressive than the average sociopath. In fact aggression was lacking entirely. That's what was most suspicious.
So she had to do something to coax out that aggression. Maybe it was a little ostentatious, challenging him to tennis. Perhaps suggestive to spectators of some other underlying relationship. She wasn't a great gauge for broad social opinion, but certainly any outsiders would assume she was out of his league, if not in academics, then in athletics and love. That would make it interesting if she were to win. Two out of three ain't bad, so to speak. Besides, his reaction would be a wonderfully sweet clue.
Still, she had promised herself to let him keep his public reputation. That she privately burned away at his conscience was quite enough. If he had a conscience at all, that is.
She really did rather hate losing.
She pulled her laces tight. Double knot.
This punk would do everything in his power to outplay her in this one set. He would probably overthink every step to try and outsmart her, as though winning or losing might have merit as far as proving his innocence. But this was no trial by combat. All that work would be for naught.
Damned if he didn't, damned if he did.