Henry would be pretty chill with everyone, not gonna lie. He'd be a little annoyed with some people, but not panicked. ...He'd probably freak out the most if Sumia arrived, because oh god future wife
do I have to do the husband thing
what even IS the husband thing
Komaeda... would not take kindly to Monobear, obviously! And I don't think that any characters from Absolute Despair Girls would work out, either, even if he doesn't know them and I haven't played the game
Oh, and he'd have a bit of a moment if Hinata showed up again too, because Hinata.
so how'd he take future daughter
He's... well really he's just rolling with it (or trying to look like he's rolling with it). He's more concerned with Cynthia's well-being than what her existence could imply for his romantic state of affairs.
and this is why all the endings say that he's a surprisingly good dad I guess
He does get upset about it sometimes.
He is! Henry's got this thing where he wants to be the bestest dad ever because yay parental abandonment. But he also knows that he's a pretty bad choice of father by virtue of being... well, him
so he's worried about Sumia showing up and worried about Cynthia's life being ruined because he was in it
Playing him is pretty much a series of one "child no" moment after another
...you seem to have a lot of characters like that
i mean, the only recent muse who isn't a case of that is Cyrus, and he's terrible for a rather different reason
Pre-RP hiatus I played a lot of characters who were basically the people saying "child no" all the time, so this is my way of branching out i guess!