Hey, an audience surrogate! A weird one, but that's par for the course in this manga. Anyone who sticks around Itai is odd, that's just the nature of things.
I don't know if she's more a bad person or a strange person, I guess we'll see. 5 boyfriends indicates the former, but she's so interested in Itai's strangeness that she just might be so bizarre that there's some sort of arrangement or misunderstanding to cause it.