I kind of feel like they're doing too many gimmicks here. Dungeons in Japan, unbalanced gender ratio, returning from defeating the demon lord. Pick one.
The art is quite good, but the story... I'm not even sure this can be called wish fulfillment, because what is even happening half the time? If the hero was so cartoonishly evil the entire time, you'd think ONE person might catch on, but apparently no???
BRO IS AN ADULT AND IS TYPING IN ALL CAPS COMPLAINING ABOUT FICTIONAL MEN ON A FORUM ABOUT MANGA. Let 'em live a little. It wouldn't be an interesting story if every character was 100% perfect right off the bat.
Oh, NOW something's weird with her sense of distance? NOW we have someone complaining about having her shirt open in front of her students? 68 chapters in? I see how it is.
I wasn't paying attention and I thought the 'boy mode' character in the post-chapter page was the character they've been stressing over the gender of. Boy do I feel stupid... or perhaps girl.
Not only is this lazy shock-value writing, it's also almost certainly a plot hole. If this is actually a flashback to where the Demon King died, that means he told his daughters to never forgive the hero... while dead. And the gate of souls or whatever hadn't been opened yet.