Kazuhiro Oyamada, a university student suffering from insomnia and health issues, returns to his family home during summer break to recuperate. However, upon arriving, he notices that his grandparents, who are supposed to be there, are nowhere to be found. Feeling something is off, Kazuhiro asks his parents about it but is met with suspicious reactions. Eventually, Kazuhiro uncovers the 'truth' behind the strange changes in his family...