The story unfolds in Old Japan, at some indefinite period in the legendary past...

Night gives way to dawn, and the sun warmly greets all living things with its comforting message of light, beauty and love. [This is the famous Prologue that opens this opera, beginning with Orchestra that is later joined by a chorus that represents the sun. Both musically and dramatically this identification of the sun as an allegorical protagonist in the opera is highly important]

At the door of her cottage, Iris, an ingenuous young girl, relates the nightmare she has just experienced and thanks the sun for dispelling her terrifying dreams. Meanwhile Osaka, a young nobleman, and Kyoto, owner of a geisha house in the Yoshiwara (the red-light district of the city), spy upon Iris in her garden, for Osaka is smitten with her and has engaged Kyoto to acquire her for his pleasure. The men leave to plan their abduction.

Iris's father, Il Cieco (the blind man), emerges from the cottage, and Iris lovingly places him in the sunlight to pray. Just then a group of young laundresses come by to do their washing in the stream that runs by Iris's house. As they attend to their labors, Iris waters the flowers in her garden, while Il Cieco prays aloud.

Osaka and Kyoto return, disguised as itinerant puppet players, leading a company of geishas, samurai and musicians. They set up their puppet theater beside Iris's garden and invite all the laundresses to their performance. Il Cieco warns Iris to keep her distance, but she is beguiled by the proceedings.

The puppet play tells of the unfortunate Dhia, whose cruel father wants to sell her into slavery. When Dhia prays for deliverance, her plea is answered by the puppet Jor, Son of the Sun (whose voice is supplied by Osaka). Iris, who loves the sun beyond measure, is mesmerized, especially by the puppet Jor. At the culmination of the play, Kyoto's geisha dancers perform a ballet, surrounding Iris, and enabling the samurai to stifle her voice and carry her off without being seen by the other girls.

As the audience departs, Kyoto leaves a purse of coins and a note to Il Cieco on the cottage doorstep, before leaving with Osaka.

Unaware of what has occured, Il Cieco calls for Iris to assist him into the cottage, and when she doesn't respond, he panics. His cries attract a group of peddlers, one of whom reads him Kyoto's note, informing Il Cieco that Iris had gone to the Yoshiwara. Believing Iris has abandoned him of her own will, Il Cieco is horrified and broken-hearted, and he begs the peddlers to guide him to the Yoshiwara, that he might find Iris and punish her.