Landlady of Narutaki Sou. She attends the same high school as Tamami. She has several different personalities that come out when she experiences different emotions, but returns to her original one after sleeping or passing out. Each of her different personalities has a different hairstyle involving the bells she ties her hair up in and each personality has a different eye color. Kozue's eye color is a bluish green. Ryūshi is her second cousin. She is extremely nice and like all of her personalities, she enjoys umeboshi. In the manga, she begins a relationship with Ryūshi from chapter 39. In the epilogue, it seems that she is married to Ryūshi, having four kids, most likely representing her other personalities. At the start of the series, she is sixteen years old and her birthday is on December 22.