H2O is a novel that surprised me almost the entire way through. At its core is a pretty simple romantic dramedy with some existential themes, but where it really shines is how well the characters and their relationships are written. I don't know if I'll be good at explaining what makes them so compelling, but what it comes down to is how invested you get into them. Everyone has deep seated traumas, and all of them feel believable and like actual problems and not just something to garner sympathy. What's more, a running theme between the characters is despite how bad they've had it they always try to cover it up and compensate for it, like how Takuma will smile through it all even when he's sad or Hayami appears standoffish to keep people getting too close to her. It's after spending enough time watching them try to ignore these issues it becomes extremely cathartic when it all bubbles up to the surface and they can't hold back anymore. The way each heroine deals with their problems feels very fitting to their relationship with Takuma, and in turn they help Takuma sort himself out.

While the main game sees all this happen while they're in middle school, the end of each route unlocks a couple of after stories that imo are easily the best parts of the game. You are now flash forwarded to when they're in college and living together, so you really get to see the effects of how they grew up. These perfectly round out the cast and help deal with some of their lingering issues that were still present.

If you're a fan of slower drama with very introspective character writing then this is quite possibly one of the best out there that I've seen, easily one of my favorite stories. Minor complaint is the common route can feel a little repetitive with the drama but it's not too long all in all.