A cat burglar named the Moon River Thief is striking all throughout Tokyo, so Miko's grandmother sends the family her precious vase to look after. Chikkun meets a little girl named Miho who seems to be looking for her family, but it turns out she's the Moon River Thief's daughter and his scout for treasures. At the same time, Dr. Bell and Giji-Giji become interested in cat burglary, and create a giant mecha cat.
