A woman’s body is discovered in Yamanashi Prefecture, and the news suggests it may be that of the missing Aoi Tachibana (Machiko Ono). Lion (Tasuku Sato) sees the news and, in shock, comes down with a high fever.

Hiroto (Yuya Yagira) takes Lion to a pediatrician but realizes, when faced with the medical questionnaire, that he knows nothing about Lion’s age or other personal details. Taking the day off work, Hiroto struggles with the unfamiliar task of caring for a sick child. Later that evening, Hiroto and Michito (Ryota Bando) learn by chance that Lion’s birthday just passed.

The two secretly plan a surprise birthday party for Lion, inviting Mio (Asuka Saito), Torakichi (Denden), and Sadamoto (Taiiku Okazaki) to join the celebration.

Meanwhile, reporter Kaede (Yuki Sakurai), who has been following the Yamanashi case, approaches Detective Takada (Hayato Kakizawa) to gather updates on the investigation. It’s then that a new piece of evidence comes to light.