He is called 'Kaoru' because he gives off natural sweet scent from his body, while Nioumiya suffuses his clothes with the fragrance of fine incense which will be called 'Niou Miya.'
天然の薫香が身から発するために「薫」、それに対抗して名香を常に焚きしめているために「匂宮」と二人は呼ばれる。