A princess finds life behind the protection of her brother and the high walls of the mansion to be quite dull, so she takes on another identity and lives in a small house in Edo pretending to be a singer but all the while she is actually a Shogunate Detective. Framed by a crooked magistrate for a crime she did not commit, Oshichi must clear her name of false charges after a woman helps to lead a prison break of the notorious Oshu Remnants. Meanwhile the magistrate, Lord Kai, conspires to be rid of her brother, Clan Elder, Lord Abe Iyo. Her only clue is an ornate dagger with a handle made of golden coins.

Two guardians of the Nijo Castle, Shioya and Kamazawa, discover a map leading to a secret passage to Edo Castle. Instead of reporting their find to local authorities, they decide to blackmail the lords who created the forbidden passage. To prove their crime, Magistrate Toyama Kinshiro launches a private undercover investigation.

Okawa Hashizo as 'Young Lord', the unlikely sleuth sets out to untangle the riddle of what went on at the Inner Palace, where a young woman who had served the Shogun came home in fear for her life. Will the Young Lord uncover the truth of what went on at the Palace, and does it relate to a series of murders that have been occurring just before the festival?

After getting permission to dig up the pawnbroker's grave, Young lord samurai was surprised to find the body was missing, as was the Gosu plate. He had a suspect in mind, and was able to use him to learn of the pawnbroker's hideout and try to piece together the parts of the puzzle. A superb and exciting conclusion to a very clever mystery story set during the Golden Age of Japan. With no easy questions and his life hanging in the balance, can Young lord solve the mystery and regain the valuable plate?

As a result of illness and unemployment, Yamaoka Tatewaki, a "Hatamoto" (or direct vassal of the Shogun), pawned his family heirloom, a valuable Gosu plate for 100 ryo. When, of all occasions, Yokogawa Dewa came to visit and asked to see the Gosu plate on May 5th, Boy's Festival. Yamaoka then sent his steward to borrow the plate back, but the pawnbroker coldheartedly refused. He died soon thereafter of an unknown cause. Soon after that, two warehouses were broken into, but nothing was taken. When Detective Shokichi seeks the help of Young lord samurai, in solving these mysterious crimes that plague the town he takes the case and immediately surmises that the thief was looking for something special. Could the answer be hidden in the coffin of a deceased merchant who had his most valuable things buried with him. The tension mounts and the mystery deepens. Can Young lord solve the case?