Yes, the series has ecchi elements, but Kyouka stands out because:
As a Level 6, her stats are monstrous. While the exact numbers fluctuate in the novels, she is consistently depicted as having: kyouka mashiba
Kyouka’s special ability is “Slave” — she can form a contract with Yuuki Wakura, turning him into a powerful monster-like fighter. But the twist: after battle, Yuuki gets to “reward” Kyouka (and later other chiefs) with a personalized ability based on his subconscious desires. Yes, the series has ecchi elements, but Kyouka
This creates a fascinating dynamic: