Of all the girls we know so far, only two have won every match we've seen them in, without ties or losses. One is Tamaki, who's boring.
The OTHER is Akemi, the only rival team girl who scored a win against our main team, who doesn't care about kendo at all and tries to escape matches and practices alike every chance she gets. I'm convinced she's the Tamaki-killer hiding in plain sight right now. But we'll probably never see that match, because Akemi would rather be doing literally anything else and Tamaki's following-strangers-into-faraway-closets habit is probably going to catch up with her sooner than later.