[When he feels her fingers at his sleeve, he puts his hand on her back between the shoulder blades, since he's picked up that that's a cue for a desire for contact. If she wants more affection, he's alright with her initiating it.]

Well, you could talk about anything, really. You could start with what disturbs you most if you need to get it off your chest, or the least of it to work into the difficult parts, or even just starting at the beginning and talking about it linearly.

[Also, he's a little suspicious of your relationship with your twin because Mayu says some things that seems to imply more than sisterly attachment, but he's not touching that at the moment because you should probably deal with her death before you deal with that.]