crying for help in the street would get police invovle, and the guy is still the kid's father and they are not married or anything so the most police would do is keep them there until the mother come.
But yea, that would prevent the situation to escalate like this but then its would not make a story for us to see
No, Japan does not know shared custody as a concept. Families have custody in Japan, not persons.
Legally, he should have no more rights than a complete stranger.
It's obviously all liberty to create drama and a kidnapping arc, and the conclusion to it by the way isn't bad, but as usual in stories with drama and conflict, there is an easy solution the characters don't take, simply because the writer couldn't write a convincing reason why not.
Could you have written a way?