Mutsuki reminds me of one of Great Teacher Onizuka's characters, who was a professor who stalked Onizuka's love interests. For some reason, the Japanese don't have any issue in building up the fact that this sort of people are absolutely creepy and antisocial, but when they're found out no one seems to care about the fact that.
Irrespective of that important flaw, the manga portrays quite likeable characters. I think Akira is one of those few male protagonists who has a spine.