Storyline
Humanity has been devastated by a mysterious disease, leaving the world almost completely empty. One month after the disaster, only four people remain alive on a floating island south of the capital: Haruto, his childhood friend Mayu Chitose, Airi Tensuiji, and his friend Ryuuichi Ariga.
Haruto wakes up on the island with Mayu standing over him. His last memory is collapsing from the illness that swept across the world, leaving him with countless questions about what happened and why the four of them survived.
The survivors must work together to stay alive, gathering information and securing food during the day before spending their evenings together. As they spend more time with one another, friendships gradually develop into romantic feelings, while jealousy, desire, and distrust begin to threaten their fragile relationship.
Haruto must decide who to trust and how to develop his relationships with the other survivors while investigating the mysteries surrounding the catastrophe. Depending on his choices and the bonds he forms, the story can lead to different romantic outcomes and endings.