Contract Sisters

Kasane Hayafuji cannot live without making trips to a certain eatery in order to see Aoyama, a waitress working there. One day, when seeing Aoyama standing out in the rain, getting soaked to the bone, Kasane lends her a hand… But the next thing she knows, Aoyama comes to her with a “sister contract”…?! (Source: Yen Press)