Anyway, I don't think that it would be his mother. I could it being both of his parents, but not only his mother, especially when his father is arguably more precious to Yuma due to his whole annoying catchphrase. Yuma mentioned earlier in the series that he believed both of his parents were alive. His mother, despite being ignored for a long time, hasn't been referred to as dead or even hinted at it before. She's just ignored for the time being because that's usually what happens with mothers in this franchise. She may appear again, but I have my doubts about it.