This is a really enjoyable webnovel. If you enjoy lots of sugar and not afraid of the diabetes, you should check it out.
Couple differences here from the novel: the mother is the one that insisted on the marriage interview. And there was also a scene where Seiji pretended to be a waiter to communicate with Haru-Chan that he was there. They had a little moment where she went to use the bathroom and they met up.
Also, that guy she was there to meet was supposed to be a middle-aged unpopular guy. The scene where he was assaulting her he actually was trying to drag her off to a suite he rented to have his way with her.