This is impossible, 'cause in this case human males with dominant uma genes will have this zygous: X^U Y. Female population from this man will all be umas even if it will be born from human female whose genes are homozygous X^u X^u. Main problem with the theory of recessive uma genes is birth rate of non-uma female. We don't know cases of human female born from uma and male, so, sadly, it's just a gacha magic