Whereas Takeo Nagamatsu's 1930 kamishibai The Golden Bat (Ōgon Batto) was Japan's first modern superhero (and had many manga, anime and tokusatsu adaptations), Shintoho's Super Giant was the first celluloid superhero, and the role model for many Japanese superheroes to come, especially Ultraman and Kamen Rider.
It was Moonlight Mask who became Japan's first television superhero when his TV show debuted in 1958.