Sorry, gatekeeper-san. The demons are always on trial due to having to take care of the princess. In fact, I'd dare say that whatever trial you try to give them will always be easier than taking care of the princess.
@parodyres
Seriously, the demons have definitely been under a harsh training course ever since the princess conducted her reverse takeover of their castle.
@zanonyn If you didn't want the hostage to take over your castle, you shouldn't have taken her hostage in the first place. Exotic pets like princesses need lots of care and attention or they can injure (kill) themselves or others (genocide).
Suya: "What are you talking about?" is in the middle of terrorizing demons for sleeping materials and circumventing/blowing through every defense measure in the Demon Castle
@Sharpedgs: Could be a girl, you know. That hairstyle isn't exclusive to females, at least in Japanese media. And the clothes are definitely Chinese-style and aren't inherently feminine (look up Chinese traditional outfits and see for yourself).