It's just their culture and the men can't stop it. The men give all their money to their wife, so much so they joke they have two bosses.
Cheating is expected there, I'm sure you've seen Japanese women saying they don't care if their husband cheats on them, because the women are expected to cheat as well. Most Japanese marriages are sexless and they pretend to care about each other to keep up public appearances.
In Tokyo there's a lot of small sex hotels where you can rent the room for an hour or so. Women in Tokyo just grab men off the street and fuck them in these hotels. Tokyo (and Japan to a lesser extent) are casual sex havens.
If you are in Tokyo expect a lot of women there to have 200+ body counts, even the young ones.
Now a lot of women are hitting the wall and their maternal instincts were never satisfied so they cart their pets around in baby carriages.
Japanese men are dropping out in droves and the women didn't even notice, because those men were invisible to them anyways.