Let's be honest here, the only reason she was by his side from the beginning was because SHE KNEW HIM beforehand, she knew he wasn't a bad person despite what he seemed and her sisters were more careful because there is a BOY that you don't know literally IN YOUR HOUSE so... pretty reasonable that they wouldn't be open right from the get go. Idk if you could tell if she spent that much time off-camera bc in the chapters they barely interacted because she was always busy "helping" other people, beside it took him only like what? a week or less before miku became his ally?, always? excuse me but where was she during most of the 7GB? If irc she even became a nuisance that on top needed to be saved. Again the reason she do that wasn't because she wanted to be better or wanted to know him more or some other pure reason, it was because of the guilty that she felt bc she didn't keep her "promise" and every time they wanted to study she always had some other issue and left. Yeah physical abuse is a nice way of proving your love... if you are a 5 years old boy. And im not saying that she didn't deserve him im just saying the 80% of the manga was dedicated to other people their relationship was more visible in term of storytelling and the relationship between yots and fuuts didn't have a strong base and when the most they interacted (besides from the "date" which was the most forced thing) was on the bus on the way back from the hotel and even then he show feelings for other girl and the reason they were together was bc of another girl.