Ano Natsu ga Houwa Suru.

A junior high student named Ryuka unintentionally causes the death of her bully. After expressing her intent to leave and end her life, Chihiro insists on accompanying her, and they flee together. When law enforcement intervenes, Ryuka abandons Chihiro and takes her own life. Thirteen years pass, and Chihiro, now an adult, remains emotionally detached, haunted by memories of Ryuka. His life changes when a high school girl named Ruka, who strongly resembles Ryuka, enters it.