Koichi Hayama is the fiancé of Suzuna Kuraki. He was subconsciously chosen as her fiance and subsequently brought to the estate to live while the Tsukimachi ceremony approaches. A tall and handsome university student, Koichi tends to clash with Suzuna, but this can be regarded as evidence of a tsundere love affair. By the effects of an unexplained illness, he is unable to recollect any of his past, including his childhood or parents. He also could not recognize the faces of women before coming to the Kuraki estate. Koichi is a frequent smoker and has a elongated scar across his chest.