Pooh-Bah now holds all their posts and collects all their salaries. Pooh-Bah informs Nanki-Poo that Yum-Yum is scheduled to marry Ko-Ko on the very day that he has returned ("Young man, despair"). Ko-Ko enters ("Behold the Lord High Executioner") and asserts himself by reading off a list of people "who would not be missed" if they were executed ("As some day it may happen"), such as people "who eat peppermint and puff it in your face". Yum-Yum appears with Ko-Ko's other two wards, Peep-Bo and Pitti-Sing ("Comes a train of little ladies", "Three little maids from school"). Pooh-Bah does not think that the girls have shown him enough respect ("So please you, sir"). Nanki-Poo arrives and informs Ko-Ko of his love for Yum-Yum. Ko-Ko sends him away, but Nanki-Poo manages to meet with his beloved and reveals his secret to Yum-Yum: he is the son and heir of the Mikado, but travels in disguise to avoid the amorous advances of Katisha, an elderly lady of his father's court. They lament that the law forbids them to flirt ("Were you not to Ko-Ko plighted"). Ko-Ko and Pooh-Bah receive news that the Mikado has just decreed that unless an execution is carried out in Titipu within a month, the town will be reduced to the rank of a village, which would bring "irretrievable ruin". Pooh-Bah and Pish-Tush point to Ko-Ko himself as the obvious choice for beheading, since he was already under sentence of death ("I am so proud"). Ko-Ko argues, however, that, firstly, it would be "extremely difficult, not to say dangerous", for someone to attempt their own beheading, and secondly, it would be suicide, which is a capital offence. Fortuitously, Ko-Ko discovers that Nanki-Poo, in despair over losing Yum-Yum, is preparing to commit suicide. After ascertaining that nothing would change Nanki-Poo's mind, Ko-Ko makes a bargain with him: Nanki-Poo may marry Yum-Yum for one month if, at the end of that time, he allows himself to be executed. Ko-Ko would then marry the young widow.