Yuko had the blessing of Raeshka, so she wasn't feeling the power of suppression from the Underground King, but Souta wasn't exempt from this.
It wasn't that she couldn't feel the suppression. It's just that she could reject the will of this monster lord because she was under Raeshka's banner.
But Souta...
Souta couldn't move his body at all. He was forced to his knees. He couldn't decline or reject the Underground King. If the Underground King ordered him to kill himself, Souta's body would move and kill himself.
The monster lord's order was absolute.
No stray monster could reject it.
That's what it means to be a monster lord. They have absolute dominance over lesser monsters.
This was the reason why Souta didn't want to meet a monster lord. He will have no choice but to grovel on the ground and follow the lord of the monster.
