Wait, Yukari is over a thousand years. How could she be a relative from the future? The hell kind of Dr.Who timeline are we using?
Well, not just a relative from the future, but Maribel from the future. That's assuming that at some point Maribel becomes lost in the past or something while on one of her trips and she becomes Yukari. Other theories have Maribel as a Yukari descendant, Yukari without memories, or a construct of some sort that Yukari becomes while sleeping (or the other way around if one prefers to think of it that way.)
Well, not just a relative from the future, but Maribel from the future. That's assuming that at some point Maribel becomes lost in the past or something while on one of her trips and she becomes Yukari. Other theories have Maribel as a Yukari descendant, Yukari without memories, or a construct of some sort that Yukari becomes while sleeping (or the other way around if one prefers to think of it that way.)
I always liked to think of it as a Holy Trinity kind of thing, where Yukari is Maribel and Maribel is Yukari at the same time. Of course, knowing ZUN, humanity will have colonised the Andromeda galaxy before anything like this ever gets confirmed.