Divorce visa. thats a new one. No such thing.
If you have a spouse visa and get divorced in the meantime you can stay on the spouse visa until it comes up for renewal. Then after that you need a valid visa such as a work visa to stay in the country. Its as if you were never married and have to qualify for a visa to stay here. Having kids doesnt give you the right to stay and work here as their father or parent either. If you have no visa you have to leave, kids or no kids. There is no “father of Japanese national” visa here.
thats why I recommend getting PR as you can stay indefinitely in the event of a divorce and they cant chuck you out when the s–t hits the fan with the wife.