Yamashina-no-Shōji (shite of act one), the old man taking care of the chrysanthemums in the Imperial Palace's garden, has fallen in love with one of the Emperor's consorts (tsure). Upon hearing the rumour, a court official (waki) serving the retired Emperor Shirakawa sends his servant (ai) to bring Shōji for interrogation. The court official delivers a message from the consort herself - if Shōji manages to lift a heavy parcel and keep walking around the garden with it on his back, then she will deign to grant him an audience. Excited, Shōji tries and tries to lift the heavy parcel, but ultimately fails. Heartbroken, Shōji perishes. Consumed with despair, he vows with his final breath to haunt the consort in the afterlife.
The servant recounts the story of Shoji's desperate love and subsequent death to the court official. The consort's plan had been to make Shōji give up on his feelings for her, so she beautifully decorated the immensely heavy parcel to make it look light.
Afraid of Shōji's curse, the court official advises the consort to pay her respects to the gardener's body, but the consort is unable to stand up, as if pressed down by a heavy boulder.
Just then, Shōji's terrifying ghost (shite of act two) appears before her. He explains his grudge against the consort who brought him only misery and despair after giving him false hope. However, in the end, Shōji manages to overcome his resentment for the consort and, after vowing to become her guardian spirit, disappears without a trace.
"Koi-no-omoni" tells the story of an old man who has fallen in love with a woman of a much higher social rank. A lowborn and weak old man desperately falling in love with a noble woman is a trope that can be seen in various Japanese folk tales. The author of this play, Zeami, created it as an adaptation of the old play "Aya-no-taiko" (probably referring to the play "Aya-no-tsuzumi" or its original prototype). The plots of both "Aya-no-tsuzumi" and "Koi-no-omoni" are almost identical to each other, the only differences being that in "Aya-no-tsuzumi" the consort makes the old man beat a drum that cannot give off any sound, and the old man's ghost retaining his grudge until the very end.
In "Koi-no-omoni", the ghost eventually becomes the consort's guardian spirit, but the ending can be interpreted in many different ways depending on the perspective.
The idea of comparing the burden of unrequited love to a heavy load or parcel appears often in the world of Japanese poetry. The play involves the use of a stage prop that represents the heavy parcel. Focusing the plot and acting on this physical object is seen as an innovation of the genre.
One of the highlights of the play are the changes in Shōji's feelings as he keeps trying to lift the heavy parcel in front of him.
His deep passion, his expectations, his determination to lift the parcel and his subsequent loss of hope - all these feelings are expressed through song, music and motion. It is a scene overflowing with tension. The second act, however, is filled with terror. The old man's vengeful ghost has a white ‘kashira’ wig, paired with the mask ‘omoni-akujō’, which has an imposing and horrifying expression. He charges at the consort with a rod called ‘kase-zue’ (or ‘shumoku-zue’), which is usually used by characters that wield superhuman powers. This play is a testament to the burden of unrequited love that can turn an old man into an evil ghost.