Qualifications
- Must be a member of either house of the Diet. (This implies a minimum age of 25 and a Japanese nationality requirement.)
- Must be a "civilian". This excludes serving members of the Japan Self-Defense Forces, as well as any former member of the Imperial Japanese Army and Imperial Japanese Navy who is strongly connected to militarist thought. Note that former military officers from the World War II era may be appointed prime minister despite the "civilian" requirement, Yasuhiro Nakasone being one prominent example.
Read more about this topic: Prime Minister Of Japan