To be fair, the demons in Frieren very much comprehends human empathy and morals, they just dont feel or care for any of them. They instead use them to manipulate humans to predate on them.
Tenma is being made into the ultimate Cuck. Never mind being made to sit in the Cuck-chair, He's gonna BECOME the Cuck-chair. That's a BRUH and a half if I ever saw one.
To be fair, the issue isn't the attractive lady. It's all the half naked girls outside the locker and the fact he is very much trespassing into spaces he shouldn't be trespassing into.
Hypnosis app-kun sends their regards. NTR authors will find a way, regardless of any canon plot shields, if they dont just go: "How about I just ignore all that?" like the Fujoshi do when canon denies their crack-pairings.