The question about having control over his powers gets under Yata's skin, but he hasn't yet shaken the association between Rosethorn and Kusanagi in his mind; his response comes out considerably less hostile than it could.

"My power's not that work, or that strong. I can control it just fine." The only people he knows of that lose control of their skills like their are either total novices or devastatingly strong.

It, rater belatedly, is enough to make him finally wonder about his second roommate.

"So... what's this Elsa chick like, anyway?"