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.
Adapted from the bestselling Japanese autobiography of the same title, this gentle coming-of-age drama concerns an adolescent boy, Boku - Masaya, torn between the inherited recklessness of his father Oton and the inherited responsibility, wisdom and emotional strength of his mother Okan. Following a period of intensely rebellious behavior, Boku learns that his mom has contracted cancer; suddenly, his mother comes to live with him in Tokyo the entire emotional landscape of his life is altered.