It's either a manga thing or a Japanese thing, and I'd guess it's a manga thing. Split families are dramatic. You often see moms “selfishly” leaving for another man and abandoning her family, while dads just have an affair (in which case the mother and child sometimes leave). Unless one parent was abusive or cruel, I'm sure that Japanese parents want their children to have both a mom and dad in their lives. Parents know that even if they don't get along, the child needs yo be with both parents.
Yeah its pretty sexist but their culture was traditionally a patriarchy. So it may be a manga thing in order to intensify the drama and feelings of the character's alienation.But also it would be something more familiar to readers raised in Japan. Emotions and plot devices like these are always exaggerated in mangas. Probably they have less opportunity to convey angst etc in subtle language. But facial expressions and exaggerated tropes like the bad mom and falling in love with rapists are ways to create similar intense feelings / sympathy in the reader.
thats horrible when you think about it
Yes. From what I read (if I got it right) until slightly after WWII, the legal family unit was mufti-generational so that grandparents or great-granparents would be legally and financially tied with grown children and their children (etc.). If children were born, they belonged to their father's family. If the wife were sent home, she went alone. If a child was born out of wedlock, it would be the father's family's choice whether or not to acknowledge him or her (but that child would be assumed to belong to the unwed mother by default). When the government and legal system was being restructured, the law started to see the family as a nuclear unit like it is in the west, but the concept of children's rights never evolved as such. Children are awarded much as property. Obviously they love their children more than things, but it's just the visitation wasn't culturally much of a concept. Suggesting a child has a right to a relationship with both parents is kind of a new concept, I guess.
I used to think that, like the rule of the last name, the children was part of the most powerful family, in other words, if the woman is from the most powerful family, her children will be part of the family... same if the powerful family is from the dad...
is scary... because I search a little more and in case of divorce the kid also divorce from ALL the family of the parent that went away... is kinda scary...

Something I don't understand and I have seen it in several mangas is that when a woman or a man leave the house and get divorced they never see again their children...
Is like they divorce their children... and I have seen several mangas where the kids are told to choose a parent and they will never see the other parent...
Not only that.... there some mangas where there are two kids and they are seoarated and never see the other one after their parents divirce.... even if they are baby ot rooo youngs to remember they don't even know they have siblings....
Is that normal in Japan?