It is possible to change of entity type from GK to KK and vice versa but not between branch and GK/KK. In fact, there is no difference in tax rule between GK and KK in Japan.
Here is a simple process for the change process from GK to KK
1. Plan KK with all information (including AOl) needed like KK incorporation document check list
2. Get consent from all members (Investor) in GK to change from GK to KK.
3. Do public disclosure in official gazette (KANPO) for at least one month and report to creditors
4. File KK incorporation to Legal Affairs Bureau with several documents closing GK at the same time
lt costs around JPY 30,000 for public disclosure and JPY 60,000 for filing KK incorporation (If it is new KK incorporation not change into KK, it cost around JPY 200,000).
