Shirou is a construction worker, weary of his monotonous daily routine. He longs for something to break the tedium of his life, and his wish is granted when a young girl named Lucy mysteriously falls from the sky, landing naked in his life. Over the next two days, Shirou and Lucy grow close, and he finds himself falling in love with her. However, on the third day, when Shirou returns home, Lucy is nowhere to be found, and instead, he discovers that his friends have been brutally murdered.
Shortly after this shocking discovery, Shirou encounters a stranger who claims to be his friend. This man reveals that Shirou had his memory voluntarily erased and that he knew Lucy before the events unfolded. To unravel the mystery, Shirou must locate five old friends, all of whom have also had their memories erased. Alongside these five friends, there are numerous others who seek Shirou's death, as well as a terrifying monster known for its brutal killing methods.
