A rather mature story that's trapped into a juvenile love story between two teenagers.

Characterization is solid. Every character serves their purpose.
Plot is about the main character travel in his past lives and every life is an entirely different arc. So it provides a way to have different kinds of narratives in a same story while it's not jarring. The manga artist managed to make almost every story (except the transsexual one which is fairly simple) emotional and memorable.

However the main storyline doesn't appeal to me a lot as it traps other pretty good individual stories into an abusive relationship between two middle schoolers. It feels like I was reading two different manga with those individual stories being the relatively mature shonen/seinen story while the main story being a shojo love story.
This contradiction is frequently a turnoff and makes it hard to enjoy the story fully.