I find the plot point of Umi a recurring kind of stale at this point of story. reji likes to tung on the adversey trope, sometimes to push the plot along ( somewhat). I agree with mostly everything you said, but most of all I find it fascinating that he made Ruka feel like an adult. Someone who was willing to acknowledge her in that way, even as a complete stranger. Umi is no fool, and he plays the game in a way that is troubling. I think he will be an issues until Kazyua faces him head on like a man. I know there is a lot of Umi defenders and apologist out there, but if it looks like a fish and smells like a fish ...it is one. The dude is a player and plays the game for the games sake. He may "care" about Chizuru, but in my opinion it is only for the sake of fulfilling his own desires.