I think he's within his right to be mad she went to dinner with another man without at least running it by him first. Had she told him and he were still jealous, then he'd be out of line. The onus is on her for not considering how he'd feel.
With Mutsuki it's debatable what her feelings are because it can easily be brushed off as in the grey area, but jesus Yayoi is romantically into her brother huh.
I understand Jamini's Boxs reasoning but it's frustrating whenever you read a bunch of series and don't know when new chapters are released because they're not updated on Mangadex. If anything, I feel as though this may end up having an adverse effect and drive people to just read it on other...