Just finished the content so far, and i'd have to say you did good with the characters, they each have personalities and motivations which helps in giving them the reasons to do what they do, so good work on those.
The problem is the MC. If there was one image that could summarize him, it would be this:
The guy has all the personality of a zombie. It feels as if the few times he shows something resembling a human emotion he's forgotten all about it five minutes later, reducing him to a wheelbarrow of plot that's just being wheeled from one scene to the next. I understand the literary device of keeping your MC nondescript in order to make the reader imagine themselves in his place, but there needs to be some baseline to work with. You've got the skill, it shows in every other character.
Crowning moment was when a certain yandere cornered him in the toilet to try and blackmail him into become her bf, and the scene tries its best to portray him as the victim when he's standing right next to a tied up girl he just creampied. I mean... time and place, right? There are a few more instances of... rather sudden emotional transitions (like when
Miki got dragged to the toilets, after which everyone forgot she existed a minute later).
Of course, this is just my personal opinion, so make of it what you will. And while i may sound harsh about the MC, the scenes and the other characters are fine, it just by contrast makes the MC so much worse.