@MolaCola I forget which chapter it was in, but one chapter had him consciously doing pretty much exactly that; I think it was in a fight or something, where his old self would have just gone ahead alone, but his new self likes the friends he'd made, so he decided to go it with them or not at all.
As for him not "hearing" her, I'm pretty sure he's just playing dumb, because his mind's still that of a 60-80 year old man, whereas these girls are all 15 or so (I think Redia's like 18-24, though? Can't remember, it's been so long); that's enough of a gap that it wouldn't be strange for him to have had grandchildren or even great-grandchildren their age. He probably just can't bring himself to think of them in that light... Yet. I imagine the longer he spends as a youth, the more he'll integrate with his younger self and he'll become, for all intents and purposes, a really talented teenager.