classic waka stream

In the deep mountains,
treading through the fallen leaves,
the stag cries aloud—
when I hear that lonely voice,
then autumn is most sorrowful.

Meaning
In the deep mountains, when I hear the cry of a stag treading through the fallen leaves, it is then that autumn feels most sorrowful.
Commentary
Book Four Autumn Poems (Part One)

This poem was paired in a poetry contest at the residence of Prince Koretada.

In autumn, stags cry out in search of a mate, and hearing their voices deepens the sense of longing, making the sorrow of the season all the more keen.
The vivid image of mountains colored with red and gold leaves stands in contrast to the poet’s lonely heart.

The phrase “treading through the fallen leaves” may refer either to the stag or the poet, but as the stag’s cry carries far, it is most natural to understand it as describing the stag.

In the Ogura Hyakunin Isshu, this poem is attributed to Sarumaru no Dayū, one of the Thirty-Six Poetic Immortals, though little is known about him.
Author
Unknown Poet
Source
Kokin Wakashu
Other