11-year-old Yusuke and his classmates camp in the woods and see a strange light. They discover a small metallic object like a robot which talks, calls himself Tetra and knows Yusuke's name. Tetra can create wonderful gadgets but actually has to save the world with Yusuke's help from extraterrestrials with bad intentions.

Three bank robbers, who declare themselves to be Space Travelers, take six persons as hostages when they are surrounded by the police. Among the hostages, there is a terrorist with a hidden bomb. In order to escape, the robbers ask the hostages to pretend to be part of the gang. Surprisingly, the hostages soon enjoy doing so. On that strange day, the bank becomes a tropical paradise...