Aki Nagisa

Three stories from Shiratsuna Island: "Mikan no hana" Shiratsuna Island is the only remaining island city in Japan, but it is being merged with a city on the opposite shore. Housewife Misato Tomita lives on the island. "Umi no hoshi" Yōhei Hamasaki, who was born on Shiratsuna Island, lives in an apartment in the outskirts of Tokyo with his wife, Tomomi, and their son, Taichi. "Kumo no ito" Popular artist Hirotaka Kurosaki, who is a native of Shiratsuna Island, goes back to his hometown after seven years.

A corpse of a clown is found in a park. Detective Shirataka Amane of Musashino Higashi Police Station begins investigating with rookie detective Uzuka Shinsaku. They find a picture of the victim holding a balloon with the number 1 and the letters TTX on social media which indicates pufferfish poisoning. Shirataka intuitively suspects that this is an incriminating statement done by a serial killer, but Chief Investigator Fukukawa Saeko denies her. Detective Kusano Seiya and other personnel of MPD First Investigative Division join the investigation, then a second murder occurs. Shirataka recalls an unsolved kidnapping and murder case from two years ago that she still regrets.