Takeshi Hongo is a promising young man with a passion for motorcycle racing. However, his dreams are suddenly ruined when he gets kidnapped by Shocker, the evil secret organization planning to dominate the world. After being remodeled into a cyborg, Takeshi escapes and swears to protect the world from the inhuman monsters.
To keep using their school's abandoned observatory as a refuge, two sleepless high school students decide to revive the defunct astronomy club.
Granutes are intelligent lifeforms that operate secretly in the human world. They kidnap people for the sake of "Black Market Sweets." As people are attacked one after another by the Granutes, Shoma, a young man from another world, rises up to save the people. Together with the Gochizo, small monsters born from eating sweets, he transforms into Kamen Rider Gavv with a mouth-like belt!
