Ushinawareta Mirai wo Motomete  

In Search of the Lost Future, 失われた未来を求めて

Kaori Sasaki, a member of Uchihama Academy's Astronomy Club, confessed her feelings to Sou Akiyama but later died in a road accident that evening. Her friends and fellow club members mourned her death at a local hospital. Despite this, she appeared at school the next day without any issues. The group continued with their plans for the cultural festival until an unnatural earthquake shook the room. Everyone split up to investigate except Nagisa Hanamiya, who stayed behind. While investigating, Nagisa noticed that her relic-like cube emitted a strange blue light. Meanwhile, Sou discovered an unconscious and naked girl in a pool of water. The story follows the Astronomy Club's increasingly bizarre adventures as they deal with ghosts and unrest between student clubs. They also try to understand the circumstances behind the sudden arrival of a new transfer student.