Yotsuyamachi, an ordinary city that can be found everywhere, there is detective agency in the corncer of the town with unusual detective.
Her name is Hyakukiya Hikari, She is a detective who fight for justice!, she also has his own office in the town. On top of that she also has the power of youkai and gives evil youkai the judgement of law!. But the most important part is her huge breasts, and her animal ears!. She often received an request to investigate a youkai activity. However Hikari is a bit clumsy as a detective. Without reliable companion, she’s just a prey in youkai’s eyes.