Tachibana is Haine's biological little brother. Upon seeing Haine, he mistakes her as their mother because they are alike in appearance. He was rude to her until he finds out Haine is his older sister;.Tachibana becomes very kind to Haine and develops an affectionate "little boy" nature around her. Kusame was jealous of him because he spends so much time near Haine. When he was born, it was expected that he would become the next heir of the Kamiya family as its only male heir. However, in the final chapter, it is revealed that Takanari, by marrying the Kamiya family's eldest daughter, Haine, would become Kazuhito's successor. He also is not speaking to Haine due to jealousy that he wanted to make her happy.