The first of two Tiger and Bunny movies, based on the first two episodes of the TV series with additional new scenes.

More than twenty years ago, an evil summoner committed "Great Summon". One third of human beings were killed, and devils and monsters invaded the Earth. One day, a painter, Tamura Fukutaro, moves into an apartment house called "Ashiaraiyashiki" and gets involved in the troubles of his non-human neighbors. It's the beginning of a severe battle among gods, devils and the ruler "The Central".

Aoba is a young girl who loves to build models of robots. She lived alone with her grandmother until her grandmother passes away. Shortly after she is kidnapped and brought to a secret base where she discovers a huge robot. The piloted robots fight against Ancient-Jinki in The Grand Savanna, but the true meaning behind the fights is hidden. Aoba works hard at the base so one day she can pilot one of the robots and discover these secrets.

The Yomota family is small and typical: father Kinekuni (42), mother Tamiko (38), and son Inumaru (17). One day, a beautiful girl appears at their front door, calling herself "Maroko Yomota," granddaughter of Inumaru who travels back in time with a time machine to visit her ancestors. Even with Tamiko's strong objection, Kinekuni and Inumaru welcome her to stay with them, and the structure of a happy family has begun to collapse.