
I think I get the gist of what you're trying to say, but I don't think it's fair to place any blame on Momo for what happened between him and his mother. Ultimately Momo was a child who was severely neglected and abused. I think him reacting to that abuse by trying to exert control over it is expected. I think part of him was even testing his mother's love for him - hoping she'd tell him no and give him some attention and care. It is not his fault that those men took advantage of him. They all knew better. I also think Momo leaving on a "good" note was not him thinking he had no right to complain. It seemed more like him realizing that although he could not forgive her, she was also a victim.
as much as i love the mother having depth and her own set of trauma, it makes me happy you as a reader aren't forced to forgive her. momo didn't either and that's fine. she's a really horrible person who failed to do the bare minimun an adult has to do when seeing a child being hurt, to help them. i still can see her own pain, however. that's a sign of a good writer, harada is top tier