Ooizumi Kanami♀

Ten years ago, Kengo's father and Kanami's mother remarried, and they became step-siblings.

Young Kanami longed for the fatherly love she had never received before, but Kengo's father was a busy man, and she was unable to build the kind of relationship she wanted.
To make up for this, Kanami grew attached to Kengo, her much older brother, like an imprinted chick.

Kengo also doted on Kanami, but this was only until he went to college, when he left home and stopped going near his parents' house.
Since then, Kanami felt a great sense of loss, and her feelings for Kengo grew stronger.

Eventually, Kanami enrolled at Reiki Girls' School, where Kengo was a teacher.
However, when she enrolled, she was confused to find that Kengo had become a completely different boy.
She is in a different class from Haruka and Mizuki.

[Translated from the the official site, archived]