Imperial envoys (waki and waki-tsure) travel to Motosu County in Mino Province (currently Gifu Prefecture) in order to inspect Yōrō Cascade - a waterfall, the name of which means "care for old age". Upon arriving there, they meet an elderly woodcutter (shite of act one) with his son (tsure) and ask him about the origin of the spring. The old man replies that one day when his son was out working in the woods, he stumbled upon this spring and discovered that its water has the power to magically restore an exhausted person's strength. He scooped some of the water and brought it to his parents. To his great surprise, they regained their youth upon drinking from it.
After hearing the old man's story, the envoys are astounded by the miraculous powers of the spring. Invigorated by the wondrous spring, the old woodcutter recites ancient stories praising the merits and virtues of wine, and eventually leaves together with his son.
Later that same day, an elderly local man (ai) comes to Yōrō Cascade, muttering the origin story of the spring to himself. He takes a few sips of the spring's water, and performs a dance in honour of its miraculous effects. Having completely regained his youth, beaming with joy, he makes his way back home.
In a different version, a Mountain Deity may appear instead.
Just then the Mountain God (shite of act two) appears. He reveals that the Buddhist and Shinto deities are indivisible, just like ripples are indivisible from the water surface, and that he is the manifestation of Bodhisattva Willow Kannon. The Mountain God blesses the miraculous spring with everlasting flow, performs a dignified and energetic dance, praises the virtues of the Emperor and his peaceful reign, and in the end returns to Heaven.
The type of auspicious Noh plays in which a deity blesses the land with peace and abundant harvest is generally known as ‘waki-noh’, or "first-group plays". Created by Zeami, "Yōrō" is among the most frequently staged and most representative of the ‘waki-noh’ plays.
In most plays of the ‘waki-noh’ type, the main character of the first act is a temporary incarnation (shite of act one) of a deity which in act two appears in its true form (shite of act two), and both roles are performed by the same actor. However, in "Yōrō" the old woodcutter and his son, who appear in act one, are not portrayed as incarnations of a deity, but as ordinary people.
Scholars assume that in ancient stagings of the play, the father and son would remain onstage all throughout the second act, and a different actor would play the role of the Mountain God in act two.
Towards the end of the first act, the old woodcutter narrates various legends, such as the story of the "Seven Sages of the Bamboo Grove" (describing seven Chinese sages who used to gather in a bamboo grove and drink wine), or the legend of the "Chrysanthemum Child" (which tells of a hermit who only drank the dew drops of the chrysanthemums in the mountains and got to live for 700 years). Particularly pleasing to the ear is the sonorous libretto, in which the miraculous current of Yōrō Cascade is referred to as "the master of all elixirs", an expression often used about wine.
In Noh, there are "special directions" that diversify the usual performances with various changes or additions. Each of these special directions, collectively known as ‘kogaki’, has its own original name.
In the Kanze-school special direction ‘suiha-no-den’, the Willow Kannon, who is usually not an acting character, appears on the stage prior to the Mountain God, and performs the dance of a Celestial Maiden. Additionally, the Mountain God is dressed in different attire and dances much more energetically than usual.