Arata returned to his hometown due to his father’s work and was reunited with his three childhood friends after 10 years apart. They were the cheerful and innocent Yuuka, the reliable ‘onee-san’ Ayami and the once-small Mikana who had now grown to be very beautiful. Adding another childhood friends Yuusuke and his moodmaker little sister Mahiru, his school life is full of enjoyment like in the past. Then they received a strange e-mail inviting them to play a game. If they did not accept it, they will lose something precious.