Yuta is bringing his family's offering to a local shrine, consisting of an octopus, squid and crab, when someone steals the seafood from him and, almost immediately thereafter, giant seafood monsters arrive to wreak havoc in Tokyo. His arch-rival, Hikoma, not only steals his formula for creating large creatures out of small ones (to solve the problem of hunger), but also steals his childhood sweetheart Nana.