[Momo's tone shifts to something a little bit exaggeratedly confused as he replies, because on one hand he knows Mikasa might be having trouble figuring things out with their comparative differences in experience. But on the other, he can't help but tease a bit.]

No? I have a spare bedroom, since Lio lives on the roof...have you never seen a couple sharing a bed before? We couldn't date back home, but there's nothing stopping us here, you know.

[He has a sneaking suspicion of what she's reading into this scenario, and he is...going to do absolutely nothing to disabuse her of that notion even if it's less accurate than he would like.]