After the fall of North Nippon, some cities were not ready to reintegrate into Japan, either due to rebels or nukes in the area. Most areas reintegrated into Japan within months of GWII. But Wakkanai, however, saw this as an opportunity. Consisting of mostly farmers, Wakkanai believed that Japan wasn't appealing to their cultual and political needs.
They declared independence, but weren't recognized by most other countries because of Japan's presence in the Confederation. They were only recognized by Sennar and Ethiopia, and even they didn't help Wakkanai. After few weeks of not recognizing Wakkanai as a state, the Japanese foreign minister approached the president of Wakkanai to get them to rejoin Japan. They refused.
After another eight weeks, Wakkanai was barely exporting any goods, due to lack of resources and sanctions from members of the Confederation. They reapproached Japan and agreed to join as an Autonomous Region.