If I remember correctly, her mom is like way down on the list of concubines, and she's like the 17th kid, who was completely ignored because she wasn't special at all, until her magic woke up.
I get most of the humor of the manga revolves around idiots doing outrageous things, but here it feels overdone. Why doesn't he just take off his boxers ?
So the Hero came from Earth, and it's Anatastia's mom who summoned the hero, which means Anatastia could accidentally have sent Naga, herself, the demon twins and the monsters to Earth.
This actually explains more than you think at first! Reading this, there were plot-points that weren't adding up.
1. How do demons know to bow when apologizing?
2. How come everyone can instantly understand each other?
The only explanation is that the language and culture of the hero 200 years ago was spread throughout the more magical world. Japanese was taken up as a diplomatic common language among all the races.