(ユカ?) is Kouta's cousin, around his age, and moves in with him at the Kaede's inn. She has had feelings for Kouta since childhood, and she reacts jealously to Kouta's attention to Nyū. However, it is later shown that she is jealous of any girl, regardless of age, who she suspects may be close to Kouta, to the point of being irrational, although in the anime, Yuka's jealousy is mostly limited to Nyu, whom she views as a rival for Kouta's affection.
At one point he reciprocates the feelings, while Kouta and Yuka are searching for Nyu (after she escapes from the Professor's lab), they take shelter from the rain at the Sasuke Inari Shrine. While holding each other in an attempt to keep warm, Kouta apologizes for not remembering anything about the time they were together as kids, but states that he remembers that he liked her then and that he always liked her. The two then kiss, with Yuka even becoming sexually aroused, and promise to always be with each other. However, when they subsequently find Nyu, Kouta and Nyu share a long hug, and Yuka immediately becomes jealous again.
Mayu once described her as the "mother" at the inn, and Kouta as the "father". Yuka does possess a caring and mature side, and seems to be protective of both Nyū and Mayu, and later Nana. It is clear that Yuka cares for the girls deeply since she, like Kouta, is unable to turn away people who have been abandoned by their parents and society. However, in quite a few ways, she is a typical teenager, particularly when it comes to dealing with her feelings for Kouta and friendships with the girls who come to live with them.
In the last chapter she is shown rebuilding the inn with the others. Ten years later, Kouta and Yuka are married and subsequently name their daughter Nyu.[