In this case, the ruling is fairly narrow and regards civil suits.
Japan has home wrecker laws like parts of the United States once did. A person who forms a relationship with someone who is married and woos them away from their spouse (or causes the spouse to divorce them on the grounds of infidelity) can be held find fiscally liable for maintenance of the former spouse and any children.
So this ruling just clarifies that in the case of prostitution (which is often not voluntary) the fiscal onus is all on the married buy sexual.
Does it make more sense if you look at it in context?
I guess I am the straight man on the thread.
Are you saying a woman who “steals” another woman’s husband can be financially liable to take care of the wife and children? That would explain the ruling. A prostitute isn’t “stealing” away the woman’s husband.