AnoHana: The Flower We Saw That Day (2015)

High school student Jinta is a hikikomori and lives in Chichibu, Saitama Prefecture, Japan. One summer day, when Jinta is absorbed in a video game, a girl suddenly appears in front of him. The girl is Jinta's childhood friend Meiko, but it seems impossible because Meiko died on a summer day. Meiko wears the same white dress when she died, but she looks a little taller. She tells Jinta that she has a wish and that's why she came back as a ghost, but Meiko can't remember what her wish was. To grant Meiko's wish, Jinta along with his friends Atsumu, Naruko, Chiriko, Tetsudo and Meiko gather together for the first time in 7 years. Jinta soon realizes that he is the only one able to see Meiko.

Unfortunately the movie AnoHana: The Flower We Saw That Day is not yet available on HBO Max.