In Oni's past life, when he was young, he made himself a mask made of coconut. He was so clingy to the mask, he would barely ever take it off. eventually, the mask started absorbing all of his negative energy, and he became possessed by the negative manifestation. Oni couldn't take the mask off, nor did he want to. he eventually died of starvation, and now, in his afterlife, he still dwells around with the mask on his face.