Kyoka, a university student, receives an old brown envelope in which she finds a photograph of her classmate, Sachiko. With this, she also finds a mysterious message saying "Help me". One day, while at a café, Kyoka overhears that "somebody had been spirited away by a man in a black suit". It was at that moment that Kyoka recalled the moment that Sachiko had suddenly disappeared in the mountains right in front of her very own eyes.