The is a keiretsu publishing group in Hitotsubashi, Chiyoda, Tokyo, Japan. It is composed of Shogakukan, Shueisha, Hakusensha and related publishing companies. The name of the group is derived from the location of its major members' headquarters in the Hitotsubashi area of Tokyo. The group companies are mostly run by the Oga family, whose influence in the companies is still strong today.