Woooow, this is the first J-drama I watch after a long time and I have to say it has reached my expectatives.
Even though the teacher-student romance thing is kinda edgy, the writers could handle it well and gave the story a realistic ending. I predicted that they would end up together right after he turned 18, but it wasn't the case. I love how she continued to pursue her dream as a teacher and went to work abroad, despite everyone was telling her she ''should just get married''. I also found interesting how Haraguchi being Bi was considered normal to all the characters and there was no issue. Her whole character was actually really cool and I liked her initiative.
Another good thing was that there were no hard feelings between the four main characters, like, between the exes, lovers, and stuff. That's really mature. I like how Hijiri and Akira's moms ended up being supportive of their children by the end of the show. Character development was definitely a 10/10!
Tl;dr. An amusing story with interesting and well developed characters, I recommend everyone to watch it, even if the student-teacher concept looks weird. :)