Adapted from the opera by William S. Gilbert and Arthur Sullivan, in imperial Japan the prince refuses a marriage and falls in love with another young woman; but a tailor has become executioner and needs to behead someone.
A chorus sings “If You Wonder Who We Are.” The Prince Nanki-Poo (Kenny Baker) tells his father the Mikado (John Barclay) that he does not want to marry Katisha (Constance Willis) as intended; but the Mikado says he must marry her within a week or die.
Nanki-Poo sees and approaches a pretty young woman, but she walks off with her family to their home. Nanki-Poo follows them and sees her guardian in an inn; but he cannot get in. He looks up at a window and plays his lute, singing “The Sun Whose Rays Are All Ablaze.”
In the morning Nanki-Poo reads an order for the execution of a tailor Ko-Ko for flirting. Nanki-Poo on the street sings “A Wand’ring Minstrel I.” Soldiers arrive marching and singing. Nanki-Poo sings with people.
Nanki-Poo asks Pish-Tush (Gregory Stroud) where he can find Yum-Yum. Pish-Tush tells him that the condemned Ko-Ko was pardoned and appointed Lord High Executioner, and he sings “Our Great Mikado.” Poo-Bah (Sydney Granville) accepts a bribe from Nanki-Poo. Ko-Ko (Martyn Green) arrives and sings “Behold the Lord High Executioner.” Poo-Bah says he is lord chamberlain and chancellor of the exchequer.
Three Maids sing “Three Little Maids from School.” Ko-Ko gets permission to kiss Yum-Yum (Jean Colin). Nanki-Poo tells her guardian that he loves her. The guardian has Nanki-Poo taken away.
In a garden Yum-Yum finds Nanki-Poo, and he tells her he is the son of the Mikado. He explains he could be put to death soon. They sing “Were You Not to Ko-Ko Plighted,” and he kisses her.
Poo-Bah gets a message from the Mikado that someone must be beheaded within one month or the Lord Executioner will be removed. Ko-Ko says he must execute someone, and Poo-Bah suggests he execute himself. Pish-Tush suggests he find a substitute. Ko-Ko asks Poo-Bah to substitute, but he declines, singing “I Am So Proud” with Ko-Ko and Pish-Tush. Ko-Ko runs and hides, and the others leave.
Ko-Ko goes outside and sees Nanki-Poo with a rope to kill himself. Ko-Ko realizes he can be the substitute and asks him to be beheaded. Ko-Ko promises him a grand ceremony. Ko-Ko says Yum-Yum will be distracted. Nanki-Poo suggests he marry Yum-Yum and then he can be beheaded in a month. He says Ko-Ko can marry her then. Ko-Ko agrees.
A gong is sounded, and Ko-Ko tells Poo-Bah and others that he found a volunteer in Nanki-Poo. Nanki-Poo and Yum-Yum sing “The Threatened Cloud Has Passed Away” with others. Katisha is carried in and sings “Your Revels Cease!” Pitti-Sing (Elizabeth Paynter) sings “For He’s Going to Marry Yum-Yum.” Katisha objects and warns them. Nanki-Poo puts his arm around Yum-Yum, and they walk off together. Katisha is carried away on a litter.
Inside Yum-Yum is being dressed and sings “Brightly Dawns Our Wedding Day.” She is reminded that Nanki-Poo will be beheaded in a month; but he consoles her as bells ring. Ko-Ko makes requests of them. They kiss, and he cries. Ko-Ko says he never can be hers because the Mikado said the wife of the executed man must be buried alive. She asks Nanki-Poo to change their plans. She sings “Here’s a How-de-do” with Nanki-Poo and Ko-Ko, who falls down the stairs. Poo-Bah comes in and tells Ko-Ko that the Mikado is coming. Ko-Ko says Nanki-Poo must be executed. Nanki-Poo hands him his sword, but Ko-Ko says he cannot do it. Ko-Ko plans to make an affidavit instead, and Poo-Bah says he will endorse it. Ko-Ko tells Nanki-Poo to take Yum-Yum and marry her. He sends them off quickly so that the Mikado will not find them.
A procession arrives, and the Mikado (John Barclay) sings “From Every Kind of Man Obedience I Expect” with Katisha. The Mikado strolls around and sings “A More Humane Mikado.” Ko-Ko tells him an execution has taken place, and Poo-Bah confirms this. The Mikado asks Ko-Ko to describe the scene. Ko-Ko sings “The Criminal Cried as He Dropped Him Down” with Piti-Sing and Poo-Bah. The Mikado says his son left the imperial court and that he is in this town disguised and called Nanki-Poo. Ko-Ko says he went abroad. Katisha sees his name on the document and cries. They bow down, and the Mikado tells Ko-Ko he beheaded the heir to the throne of Japan. The Mikado tries to remember the punishment for killing the heir. They make excuses. The Mikado says they will be executed tomorrow after lunch.
Ko-Ko and Poo-Bah argue. Ko-Ko says they must bring Nanki-Poo to life again. Ko-Ko finds him and tells him he has been reprieved because he is the son of the Mikado. Yum-Yum says he is married already. Nanki-Poo asks Ko-Ko to persuade Katisha to marry him. Ko-Ko does not want to marry her, but Nanki-Poo sings “The Flowers that Bloom in the Spring” with the others.
Ko-Ko finds Katisha in a garden and begs her to marry him. They hear a whistle, and Ko-Ko sings “Willow, Tit-willow.” Katisha calls to him, and they embrace.
The Mikado summons the gentleman and his accomplices, and they bow to him. Katisha begs mercy for them and says she just married Ko-Ko. Nanki-Poo and Yum-Yum come in to show that he is alive. Ko-Ko tries to explain and says the Mikado’s word is law. The Mikado says it is satisfactory and smiles.
This farcical operetta has pleasant music while satirizing some formalities of Japanese culture while the natural currents of romance take their course.