Good read. Koharu was a little too perfect though. She never tripped, she never broke down crying. Even if a kid tries their best, they get overwhelmed and do things they end up regretting sometimes. Sweetness and Lightning handled that better.
Also I'm disappointed that we never actually see Kazama develop any feelings for Katagiri. We just assume she keeps trying and he learns to love her which sounds like torture. It's as simple as a single scene of him reminiscing about her or the light catching his eye as he looks at her. Some inkling that he can even think about other women beyond an abstraction of moving on.
Finally, no one ever acknowledges that Youko essentially planned for Kazama to never meet his daughter, and deprived Koharu of a family, even time with her grandmother, out of a twisted inferiority complex. If it was the other way around, it would be abduction.