Shoma, who comes from a different world, is saved by a boy named Hajime when he collapses from hunger. Shoma excitedly eats the snacks that Hajime gave him, but as soon as he does, Gochizo are born one after another.

Meanwhile, freelance writer Hanto is gathering information on the appearance of "monsters" while doing research.

Hajime hides Shoma in his secret base and hurries home when a mysterious man appears before him. The man transforms into the monster Granute and approaches Hajime.

Shoma tries to save Hajime, but he is no match for the Granute. Gochizo suddenly appear in front of the suffering Shoma. Shoma sets and eats the Gochizo! He transforms into Kamen Rider Gavv and confronts the Granute!

Shoma, who has collapsed from hunger again, is helped by Sachika, who runs an anything and everything general store, and treats him to lunch and snacks.

Hanto, while working on a case story, discovers information about Gavv on a social networking service. He starts interviewing witnesses.

Shoma is asked by Sachika's friend Ritsu to assist her in her "anything goes" job.

That night, Shoma is led out by a Gochizo, who suddenly appears, and runs into a man dressed in a jogging outfit. The man transforms into a Granute, and Shoma transforms into Gavv, and they clash!

Shoma collapsed from hunger and was saved by a mysterious monster. Is it a new Granute? Shoma wakes up and transforms into Gavv, but his movement was halted by an unexpected reaction: "The surgery was a success!" Who is this monster?

After receiving a report from the Gochizo, Shoma once again confronts the Agents. He transforms into Gavv and clashes with the two Agents. Hanto, who was watching the scene, is rescued and desperately pleads with those who fear Gavv's appearance, "He's not a monster!" He desperately appeals to the people who are afraid of Gavv's appearance, but...