With whom does Junpei have his last significant relationship in "The Kidney-Shaped Stone That Moves Every Day"?

Junpei's second and last significant relationship narrated in "The Kidney-Shaped Stone That Moves Every Day" is with a mysterious woman named Kirie, who is eventually revealed to be a tightrope walker and a window washer. While Kirie holds back and only shares a brief time with Junpei, she clearly makes an impression.
Junpei's father told him that every man meets exactly three women who will be significant in his life. Junpei was haunted by this theory, and after his first significant relationship ended poorly, he was withdrawn in relationships, not wanting to waste another of his significant women.
Junpei tells Kirie of a short story he is writing about a doctor who is haunted by a kidney-shaped stone that moves every day. While this is the central symbol of the story, Junpei is unsure of what it means. Kirie vanishes from Junpei's life suddenly, and now, both the kidney-shaped stone and his father's theory of three "significant" women haunt Junpei.
While we might expect the story to close with Junpei's third significant relationship, it instead ends after it is clear Kirie has moved on and before another significant woman appears, with Junpei deciding that he is done with his father's theory and done holding back. Thus Kirie is the last significant relationship of the short story but not necessarily of Junpei's life.