Usotsuki Kusuriyubi

From Nagareboshi Manga:
Emi “Niko” Nikogawa has just entered Lotus High, a school where new students receive a ring upon entrance. There is, of course, a legend surrounding this ring– if you trade rings with the person you like, your love with continue eternally. But what happens when Niko trades rings through odd circumstance, and with a boy who says he’ll never love anyone…?!