Four years before Silent Parade (2022), Yukawa and Kusanagi investigate the murder of a writer after a video found in his possession piques Yukawa's interest.

In the sleepy town of Manazuru, a renowned physicist is called upon to investigate the death of a local man. As he delves deeper into the case, he uncovers a web of secrets and conspiracies that threaten to unravel the peaceful town. With his eccentric genius and sharp intellect, he must navigate through a labyrinth of clues and suspects to solve the mystery and bring justice to the victim.

This is an episode of Galileo in name only, since this story focuses exclusively on Utsumi Koaru, played by Shibasaki Kou. The eccentric scientist makes a cameo appearance in one scene and the final scene is on the same day as episode one of the second series, but apart from that this drama has little to do with the rest of the Galileo canon.

Physicist Manabu Yukawa returns to Japan from America. Detective Kaoru Utsumi visits him and talks about a case. The case is about a popular girl in a town who disappeared and, several years later, her body was found. A suspect was arrested for her murder. That suspect was previously arrested for another girl's murder, but he was released due to a lack of evidence. Detective Shunpei Kusanagi investigated the prior murder case. The same suspect was then released due to a lack of evidence for the most recent murder case. The released man returned to his town, where everybody hated him. On the day of the autumn festival parade, the man was killed. Physicist Manabu Yukawa, Detective Kaoru Utsumi and Detective Shunpei Kusanagi work together on his case.

When a renowned physicist becomes the prime suspect in a murder, a brilliant mathematician works to unravel the mystery and prove his innocence. As the investigation deepens, secrets are unveiled, and the truth becomes ever more elusive.