Come on. This manga hasn't been that bad. It's not dumb for most of the chapters. It's just this hyper-dumb character, that takes the cake and drags the story of the whole manga down. This character is just so f*cking stupid, it's nearly a superpower. If you add such an unrealistic element into a story, that tries to be a halfway realistic highschool drama, it just jumps the shark....the question, that remains is, "Is it salvageable?"
No...there are still other open questions. For once, "Have those other girls been equally stupid?"