Japan is a country in the Far East of Earth. It is one of the few named Earth countries within the stories of Sonic the Comic, others being the United Kingdom and the United States of America. The entirity of the Shinobi was set in Japan, primarily in Tokyo, although Musashi visited the Ibakari Province in the first main installment. The first main insallment of the Eternal Champions series was also set in Japan, which saw the heroes infiltrate Nakano Industries to stop the production of the Bio-Key.
Sega, the company behind Sonic the Hedgehog, have always been based in Japan.