Residing within Tokyo's district of Ueno are the Colors, three individuals who protect their city by performing good deeds and aiding their community. Or, at the very least, they pretend to be the city's defenders. In reality, the Colors are just three young girls: the shy Yui Akamatsu, the noisy Sacchan, and the video game-loving Kotoha, who spend their time playing make-believe and exploring the city. The Colors' activities are facilitated by the grandfatherly Daigorou "Pops" Kujiraoka, who uses his store's inventory of knick-knacks to entertain the rambunctious trio.

Not everyone is a fan of the Colors though. The local policeman Saitou just wants to deal with his regular duties, but he often finds himself the target of the Colors' attention, having been made the villain in most of their fantasies. But despite his personal feelings, Saitou always finds the time to go along with the three girls' games. Even though the Colors do not actually defend Ueno, they definitely help brighten everyone's day.