In a rainy night, the cops are investigating a bizarre murder scene. "What he saw?" - wonders the detective. Takuto, the protagonist, is a sickly highschool student with a heart disease. His father is a scientist and researcher who is traveling overseas. Even thought he is alone in home, his neighbor and university student Rin come visit him every day, and every night his father call him and they talk by phone. But one day, his father stops calling and they lost contact. Takuto wonders if something happened to him and contacts the laboratory where his father works. But the staff members dont' know anything. Takuto is worried, until one day a strange girl called Eryu appears in his house with a letter from his father. "I'm sorry ------" - Says the last words of his father. And something who don't look to be human starts to approach the hero, who little by little get caught in the case of the bizarre murders. And seeing the disturbing signs --- a heartbeat began to drift. [Translated from Getchu.com]