Adapted version of Japan's historical event during the Bakufu Era, Princess Kasu no Miya had to marriage Shogun Iemochi for political reason. Before the marriage ceremony, she wants to meet a boy she met when she was little once for one more time. Princess Kasu no Miya runs away from her guards and meets Ishinosuke and Sakon who opens their detective business on the street.
Without telling them who she is at first, she hires the two to fend off her guards and later after her truth identity revealed, she continues asking them to help her find her first love. With time running out, will Sakon and Ishinosuke be able to find that man? Who is that boy Miya fell in love with back there?