If it helps, think of it like this: There's an alternate Luceti where 25 year old Yuber the Zexen Knight arrived instead of demon Yuber. His interactions were very similar to demon Yuber, but things happened for different reasons. He only killed Vash out of self defense, for instance. Now, for this week, you're going to play as that Yuber in this Luceti. So no extra hundred years need to be forgotten, because this Yuber never had those.