[If Atsushi knew it was Mikazuki's house, he would be quick to reassure Slaine no end. As it is, he can only work with hypotheticals.]

Well, that's easy. Just talk to them!

[... Okay, maybe not that easy. But it's perfect in theory!]

If you're not sure what they're thinking or what they like, it can't hurt to ask. They don't have to answer if they don't want to, but at least it will show that you're trying to understand them.