Yui Narumi (成海 唯 Narumi Yui) is a classmate of Kou from junior high. Her father was in the same hospital as Kou's mother. She was once a Genki Girl and popular at school until her father's death has left her very disillusioned. This event naturally brings her close to Kou, who has gone through the same experience, and threatened by his relationship to Futaba.

Personality: In middle school, Narumi appeared do be a very kind person, considering how nice and understanding she was to Kou. Narumi acts very hopeless around Kou, in order to get his sympathy so he would stay by her side. She feels as if Kou is all she has, so she acts selfish to the sense of keeping him to herself. 

Narumi can be very conniving, for instance she was trying to convince Futaba not to worry about the accidental kiss during the school festival, because Kou and her in fact also kissed (this was her attempt on trying to break Futaba away from Kou). She tried to fool Futaba with her fake personality, but later reveals her true self and lashes out when Futaba came to confront her about Kou.