Set in the fictional Japanese town of Titipu, "Mikado" tells the story of Nanki-Poo, the son of the Mikado of Japan, who has fled his father's court after falling in love with Yum-Yum, a beautiful lower-class maiden. When the Mikado learns of Nanki-Poo's whereabouts, he sends his Lord High Executioner, Ko-Ko, to Titipu to behead him. However, Ko-Ko is a bumbling and incompetent official, and he soon becomes embroiled in a series of misadventures that prevent him from carrying out his duty. Meanwhile, Nanki-Poo and Yum-Yum are aided by a group of eccentric townspeople, including the elderly Pooh-Bah, who holds multiple government positions, and the dim-witted Pish-Tush. Together, they devise a plan to outwit the Mikado and allow Nanki-Poo and Yum-Yum to marry.