How many times will hiromi have to display that he's not interested in these girls WHILE HAVING AN ACTUAL GIRLFRIEND before they get off of his case?
The problem is that Hiromi himself isn't actually displaying that he's not interested.
He's overly familiar with all of them, does nothing to disabuse them of the misunderstandings that lead to them developing feelings for him, and when any of the actually act on those feelings--Tsubasa drunkenly stripping in front of him, Lily wanting to date him despite the actual rules of the sharehouse, Anju
forcing herself on him while he's talking to Konoka on the phone--Hiromi never pushes back and just lets them do whatever they want, giving no indication that he wants boundaries around acceptable behavior or
actually saying "
I'm not interested in a relationship".
Don't forget--the only person who knows he's dating someone is Anju. And she proceeded to strip and then force a makeout & groping session on him, mid-phone convo with Konoka. When they were discovered by Mio, Hiromi
took the blame for Anju's behavior instead, and that was after doing nothing to stop her from SA'ing him in the first place.
None of the Sharehouse Five have any reason to believe he's not actually interested in each of them, because his behavior lacks any propriety, he gives every nonverbal signal that suggests he's okay with at least casual intimacy and affection, and he's said nothing whatsoever about dating or not dating them.
He's an idiot who refuses to make hard choices because he thinks it'll hurt someone's feelings, so he avoids confrontation at all costs. And the result is a powder keg of a shared house that risks blowing up all of their relationships with one another.