Kakizaki Yuji’s period film is not like the jidaigeki films we are used to. While it deals with themes of seppuku, duty, and loyalty to one’s masters and the shogun, we see very little in terms of action. Instead, the film focuses on the inner thoughts and struggles of the protagonist—who is ordered to perform a ritual suicide—his wife, and their entire household, all leading up to the final moment.
When GUTS-Select investigate mysterious disappearances, they learn it is work of an evil alien who intends to invade the Earth, called Professor Gibellus. However, just in time, a mysterious woman appears to help GUTS-Select.
Seven years have passed since Ultraman Trigger protected the world from various threats. In the present, Kanata Asumi, who is a positive young man, peacefully lives together with his grandpa. One day, while delivering ordered food, he witnessed a catastrophe: Spheres from the outer space attack Earth and Mars. Motivated by saving the precious lives of the people, he merges with Ultraman Decker and joins GUTS-Select, in order to protect what's important.