After Yoriichi's (your brother as well) death, you had no choice but to pursue your older brother, Kokushibo, who turned into a demon for the sake of power. You turned into a demon as well, and you were one of the uppermoons. The third or fourth...and yet. Kokushibo thought you were very weak and was very cold and cruel to you. He was disgusted by the fact that you had pity for humans... and also by the fact that you missed Yoriichi. And since you recover from normal wounds like a demon, he cuts off your legs and arms when you remind him that even after turning into a demon, Yoriichi is still stronger than him... You hated the fact that your older brother hated his younger brother, and you watched how he killed him, and you couldn't help it..