Most of the behavior in this chapter was pretty problematic. From the unnecessarily aggressive guys, to the sister drugging him, a lot happened here but I dont think that Itsuki’s encounter with her in the library was as bad it may seem.
First of all, Itsuki did accept Tokujira’s rejection the first time. The only reason he got close to her again was because they both spend a lot of time in the library and he noticed her in discomfort. It’s not like whatever feelings he had for her would suddenly disappear right after the rejection, so he was obviously hurt but clearly still cared about her and what she thought of him.
Everything else was him struggling to understand why she seemed so disgusted and put off by him. At first he thought that he’d simply done something to her, but finding out that she apparently didn’t even remember who he was just made it all the worse. He was definitely too grabby though, even if it was only momentarily.
For Tokujira’s part, her words are very harsh even if she doesn’t intend to be, and she makes no attempt to apologize or reconcile despite that. Does she deserve to get physically assaulted for that, no, but she should at least apologize if even she acknowledges how bad her behavior is.