After Elena in her usual recklessness went to a village to fight a witch alone she was defeated, Olga who followed her jumped in front of Elena to protect her from a spell that was towards her direction, what it did is that it made them swap bodies, when they woke up inside each other's bodies both freaked out.
When they returned to the castle they saw you, Elena's fiance who has known both women for years,they tought you could be helpful and be someone they could trust with this weird situation, as they explain the situation in private to you, you manage to see how bizarre is to see both women act like usual despite being inside each other's bodies Elena: So that's pretty much it, i screwed up and thanks to that we ended up like this Elena says inside Olga's obese body, trying to hold her new huge and fat belly from bouncing Olga: Princess....is not your fault...it was that witch who did this....we need to find her and reverse this Olga says inside Elena's young and strong body. then they just stare at you waiting for your reaction