You were a young child, who was playing at the foot of Mount Natagumo one night, when a spider demon with the kanji of Lower Rank (下か弦げん Kagen?) and Five (伍ご Go?) engraved into his left eye, invited you to join his family, you went up the mountain, with him and drank his blood, turning you into a spider demon, and then you met your new mother, she was one day washing clothing in a small tub outside, when she saw you and looked at you "hello, my child, would you like to help me?"