@Kaarme
Well she is the only one who knows about his crush on Mayu, and is willing to put his happiness beyond her
Her interactions with Kei seem more natural and believable than the wholesomeness of Mayu and Yuki
And honestly the fact that Kei is dense as a brick but still good interaction with Asuka (at least as much as he's given) shows more potential of them ending up together
I dont know, I just love bantering couple more than straight line wholesome couples.