Sara Ayafuji is a second-year high school student who has just transferred to Fujigamine Academy. Since childhood, she has been a shy and nervous person. If someone so much as calls her name, Ayafuji's face turns bright red, rendering her unable to speak. Therefore, she decides to make friends at the academy, but even with her tireless efforts, she simply cannot achieve her goal.

Nearly a week after transferring, Ayafuji is fresh out of ideas—that is, until she meets Iris Kagen, a third-year student and the student council president. Kagen is beautiful, hardworking, and admired by all; she is a proud individual who does not let many people come close to her. However, Kagen harbors a big secret: she is a vampire.

When unexpected circumstances lead to Kagen sucking Ayafuji's blood, Ayafuji finds herself marked as Kagen's bride. Day by day, the two girls grow closer, and over time, they develop feelings for each other. As it turns out, playing the role of a bride will not be as simple as it seems, and Ayafuji may have to give up more than just her blood to stay with Kagen.

Kyuuketsuki-chan x Kouhai-chan was published in German by Altraverse from April 18, 2019, to May 15, 2020.