I genuinely hate how he treated his mom tho T^T like she seems so sweet

I relate to Kuga a lot because my mom is also like that. You get so overwhelmed with their love (and all the accompanying helicopter parent issues) to the point you become suffocated by them. It sours the relationship quite insidiously, most times beyond repair. In those cases, loving them from afar is the best for both the parent and the child, so Kuga was right to distance himself from the situation.