Shinpei is a toy maker in the Kawasaki district of Tokyo. He is a neighbor and friend of Ichiro Miki and his parents. When Ichiro Miki comes home from school when neither parent is home (which is often) Miki must collect his apartment key from Shinpei's apartment. during the film, Shinpei is trying to sell a used car. When Ichiro's mother learns that she may not be home until the following day, she contacts Shinpei. Shinpei then informs Ichiro, and invites him over for dinner. Later, after Ishiro had gone home, the police approach Senpei to ask about some bank robbers who were still at large after stealing ¥500,000,000. The next day, Shinpei tries to check on Ichiro, only to find that the door to the Miki's apartment is locked. Shinpei travels downstairs to talk more with the police. Shinpei is seen again when he discovers his missing car in an abandoned building's lot. upon entering the car, he finds the stolen money. he alerts the authorities and the bank Robbers are caught. Shinpei explains to the reporters whom Ichiro had told that Minilla had aided him inside the building, that Ichiro likes to pretend that he is on Monster Island with the Kaiju found there.