To Kou and Frey their own personal hells. I mean yes kou gets a reward of sorts but, still could any one of us male readers actively go into an all girl's hot spring as the sole male? The intimidation factor would be immense. Perverts may be able to have the guts to do it but a regular guy? Nah that would be a hell. even if they could get away with it the situation would be like "Do not want to be here.. I feel like I'm being focused on way too much here.. please let me leave" I mean at least in my opinion.