I know rejuv is an anime but your japanese translation made me chuckle a bit(in a good way)
Nothing much to add as i don't think we have any element to discriminate an answer over another, though i never thought that xenadin could be the yvetal.Though it would seem odd since
when you dive in the sheridan wetland laboratory that talks about how yvetal is in a cocoon now, madame x note speaks of it with hostility, as if yvetal or the person that gave it to her is her enemy, yet if she is defeated she will say "i m sorry father" so it seems quite contradictory