Yuukaku meant the regions in Japan where brothels recognized by the government are situated. In theory, prostitution was only legal in the Yuukaku region, but there were some places where prostitution was provided illegally (e.g. Okabasho ).
In January 1946, GHQ issued an order (SCAPIN 642) nationwide to abolish Japan's licensed prostitution system, and the brothels in Yuukaku had to change their name to café or ryōtei , which transformed the Yuukaku into Akasen regions.
After the Anti-Prostitution Law was enforced in 1956, prostitution became banned in Japan, and as such the Yuukaku finally came to an end, though illegal prostitution still continues in Japan.