@pjthomas404 Yeah, memories are what makes a person... and since he and Miharu were children he's had decades more of them (nearly 30), all of them while young and malleable. He really isn't the same person she knew at all.
Of course, that goes both ways; she's grown up too. And they've had a few weeks here and there getting to know each other again and it turns out each still cares for the other.
Of course, since Rio does still care for Miharu but assumes she wouldn't accept him as he is now, and because he's got his quest for revenge against a dangerous sociopath who knows of his existence now, he's emphasizing the differences between himself and Haruto to protect her memories of Haruto and to put distance between them.
Now this is all futile, because Aishia's been grooming Miharu for weeks to accept Rio as Haruto aided by Rio having the same core as Haruto, but he's ignorant of that. For all the Aishia has been prepping Miharu with flashbacks and such, she's done nothing for Rio but give him baseless encouragement.
...Back to your comments;
He's got no trouble wrapping his head around Haruto's morals no longer working; that's been settled since Yagumo if not earlier. What he doesn't understand is that Miharu is also able to adapt, especially if it's for Haruto. (Or maybe he doesn't want to consider that Miharu would change herself for him, or grew up enough to no longer see things in black and white)
His plan is not to abandon the girls around him; it's to get rid of them after finding them better homes; in Galarc w/ Satsuki, in Centostella w/ Takahisa, or just do exactly what he did a few books ago and ship them back to the Spirit Folk. I mean, Miharu, Aki, Masato in particular are not his companions; they're explicitly in Galarc to decide on who they're going to live with. Sara, Orphia, and Alma are on a field trip but will eventually go back home w/ Latifa. And he's already made a vow to take Celia back home again to talk to her parents.. Of course, his plans have.. Of course, his plans have... never gone as such. (Plan A only works if the reader is kept in the dark)
TL;DR: I think it's pretty reasonable for Rio to want to find a safe and stable life for a girl he was fond of thirty (subjective) years ago, and then put distance between himself and her so he can get back to what he wants to be doing without endangering her or poisoning her memories of Haruto. It sucks for us readers who want a harem, but what we've got here is a harem protagonist who actually plans how to get rid of his unwanted harem.
(I'd make my points more coherent, but at that point I'd just be regurgitating the book...)
