Tsukihi Araragi (阿良々木 月火, Araragi Tsukihi) is the younger of Koyomi's sisters and the youngest member of the Araragi family. She and Karen are nicknamed Tsuganoki Second Junior High School's Fire Sisters (栂の木二中のファイヤーシスターズ, Tsuganoki-Ni-Chū no Faiyā Shisutāzu).