Brave Police J-Decker returns the series to a subtly lighter tone, focusing more on the concept of "robot as human-built AI construct" emphasized by the previous season's series, Brave Express Might Gaine. Grade schooler Yuuta Tominaga stumbles upon Deckerd, a humanoid robot under construction by the Japanese police, built to fight advanced forms of crime. Yuuta's constant contact with Deckerd gives the robot a "heart", or personality; when Yuuta is recruited as the "boss" of the "Brave Police" as a result, a true human/robot partnership occurs.