Mizuki's father is just as androgynous as Mizuki himselfIf not moreso. It would go a long way toward explaining just why he was so insistent on Mizuki being manly as a way to deal with his own issue. It's either something he wished he could do or what ultimately worked for him.
- We finally see him at the end of chapter 49 pretty thoroughly ruling this out.
Mizuki Likes Being A GirlBut can't admit it due to being scolded, coached and even abused by his father. Mizuki's recollection of trying on girl's clothing and being locked in a shed are matched with some PTSD, and he seems to pursue 'manliness' more out of fear than actual desire. As the series progresses it looks more and more like the actual happy ending will be Mizuki remaining a girl and dating Takeru.