One day after school, Asahi Kuromine discovers that Youko Shiragami, whom he has a crush on, is actually a vampire. According to her father's rules, she must leave school to protect her family. However, Asahi does not want her to go and promises to keep her secret. Unfortunately, this proves challenging for him as he is an open book and cannot hide anything.
As the story progresses, more supernatural beings enter his life, forcing him to conceal their identities or face dire consequences. Through it all, Asahi struggles to maintain his silence while also trying to win Youko's heart. Jitsu wa Watashi wa follows Asahi as he navigates these challenges and learns valuable lessons about trust, loyalty, and the importance of keeping secrets.