Try visiting bedrooms and stuff as if they where recurring events. I think there are a few '!' missing here and there. That is a kind of a random event that happens in the household like when Ain goes around in a towel.
i think you need to go to dining room and tell Emilia, that you're waiting for dinner or something.
Pretty sure he's your former desert stalker mentor, who walked off into the desert and has now reappeared as the lord of the decayed (if that's what they're called? they might be called something else?)
That probably depends what choices you've made earlier. But im not sure which ones.
