Sixteen-year-old Kanoko Urabe knows that someone is lying if she can hear the strange, echoing sound of clanging metal in their voice. As a young and overly honest child, she would point out the lies of other villagers, and was ostracized as a result. She is eventually forced to leave her hometown and tries to find a place for herself in the city of Tsukumoya in 1920s Japan.

In a chance encounter, Kanoko meets Souma Iwai, a gifted but penniless detective. After she is forced to demonstrate her ability, he expresses appreciation for what she can do and agrees to take her in, asking the girl to be his assistant. The Iwai investigation firm soon makes a name for itself helping clients by solving cases with Souma's sharp wits and Kanoko's power. In the process, Kanoko's life is enriched by the various people she encounters in her investigations.