He wasn't eavesdropping, not really but the fact Nanami left the apartment was enough to have him waiting on the couch for when he returns. He's aware Nanami hasn't told him everything and he hasn't really asked much about the future.

Because it doesn't really change what's happening here and when Nanami's ready to talk he will. But from the sight of the girl, and yes he'd seen her before disappearing into the bedroom, stuff was probably worse than he'd suspected.

There's also tea waiting on the table.

"....Are you okay?" It's quiet, concern in his voice.