The story centers on grade schooler Nanoka Koyanagi, who meets a short-tailed cat and three different women as she is out taking a walk. The first woman is Minami, a high schooler whom Nanoka sees has many wounds on her wrist. The second woman is another high schooler, constantly called a "whore" by her classmates. The third woman is an old lady, trying to live out her twilight years in peace.

About the quiet high school student Kyou who has a special ability...

One day, I—a high schooler—found a paperback in the hospital. The "Disease Coexistence Journal" was its title. It was a diary that my classmate, Sakura Yamauchi, had written in secret. Inside, it was written that due to her pancreatic disease, her days were numbered. And thus, I coincidentally went from Just-a-Classmate to a Secret-Knowing-Classmate. It was as if I were being drawn to her, who was my polar opposite. However, the world presented the girl that was already suffering from an illness with an equally cruel reality...