@tgb089 yeah, kinda weird she's the demon king but so weak.
Only possibility is that everyone in the world got weaker. the first demon kings being strong but later on maybe going to the 30th or maybe 50th onwards getting weaker. arriving at the "current" power level.
He is just at the level of the first few demon kings and she is just in name since she is the strongest atm.
Oh well, here we go. It would been a lot more interesting if he beat the dragon with some gimmick and strategy instead of just overpowering it outta nowhere.