The protagonist, Nakaizumi Yuuji, and his girlfriend, Kiryuu Miori, attends the same university. But one night, Yuuji went to visit Miori but heard a strange voice coming from his girlfriend's room. Feeling uneasy, he peeked inside the room and saw Miori in the arms of another man. Dumbfounded, he went out and wandered on the road. He noticed a car coming, and as he was hit he lost his consciousness.

When he woke up, he was in his room. He was relieved that it may all have been a dream, but soon noticed that no one can see him and his body was like that of a ghost. Moreover, the world look exactly like it did two years ago. Thinking that he was simply lucid dreaming, he looked around and saw Miori, who he then followed. He then witnessed Miori having sex with her then boyfriend. He woke up soon after and realized that he has indeed been in an accident, but he still kept having dreams of him going back to the past. In those dreams, he always saw Miori with another man.

He saw one where Miori was cheating on him with her ex-boyfriend, and also saw another one with the man he saw with her on their anniversary night.

"Is this just a nightmare, or am I really seeing what happened in the past...?"

[Translated from Official Site]