How about he ends up meeting and getting protective of a few new friends? Then he finds himself softening up towards them, alongside his sister? I personally think that if he ends up meeting a soft-hearted girl, he’d fall in love at first sight. And that a kind-hearted boy with a massive hero complex becomes his best friend (and favorite person besides his sister to cling to). And that an older girl with hypermnesia that allows her to memorize and repeat entire conversations (with timestamps, too!) becomes his best female friend.