Shinkichi is a youngster living in Odo Island along with his mother and older brother Masaji, the only survivor of the wreckages of the Eiko Maru and Bingo Maru fishing boats caused by Godzilla. Shinkichi is first seen serving as a lookout with one of the village elders, and spots his brother's raft landing on Odo Island's beach. Later during the night an exorcism is performed on the island in an attempt to prevent Godzilla from attacking the village, a storm begins and his home is destroyed during Godzilla's initial rampage on Odo Island with his family trapped inside, causing him to become an orphan.
Shinkichi is brought to Tokyo along with a group of survivors of the raid as witnesses to report the attack.
During the investigation of Odo Island, Dr. Yamane visited the grave of Masaji and his mother, victims of Godzilla's raid, and met Shinkichi. Yamane later adopted Shinkichi as a son.
Shinkichi is later seen living among the Yamane family and occasionally accompanying Hideo Ogata. Shinkichi is last seen among the people present in the ship sent to use the Oxygen Destroyer on Godzilla.
Though Shinkichi never appears in the film, he is mentioned several times. It is revealed that Shinkichi went on to become a famous scientist, who dedicated his life to studying Godzilla. He fathered two children, Yukari and Kenichi. Sometime before the events of the film, Shinkichi had passed away. Kenichi said that Shinkichi always expected great things from his children, and that if he were alive today, he probably wouldn't be very happy with either of them, as Yukari had become a reporter and Kenichi was a college student who studied Godzilla only as a hobby. Kenichi and Yukari would go on to play very important roles in trying to save the world from Godzilla's meltdown.