From Nagareboshi Manga:
Yui has a deep love for her "older brother" (they're not actually siblings, but are related), and she is devastated when he gets married. While at the wedding, Yui meets a sobbing boy, Kaoru. It turns out that his cousin (that he was in love with) is the one Yui's brother is marrying.
When Yui moves into a boy's dorm so she can seek out new love, she…
SUGIYAMA Miwako
Related works
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…