I’ll go with the spirit

I'm certain that he had to share some of his spiritual “life” with Uke - since he had already stepped on death. They have the deal, and although he was young when he made it, he has to honor it. Broo wished for someone and the mountain spirit can't grant that ‘someone’ when he had nothing else aside from his jackass father. Uke being cast out by people must be because he's half neither dead nor alive. He's sharing the mountain spirit life already which isn't human.