Which universe is the real?

Kim Taehyung never could appreciate what he had received from life. Neither as a young and talented prince at the ancient Silla, nor as one of the seven deadly Sins. And it doesn't change during the WWII, either.  When Hitler's closest men find the lost box of Pandora, the situation offers him a perfect opportunity for enslaving his fellows. Although, there's something he wasn't aware of.. Pandora's box is more mighty than