When you have more than 1 QT willpower, the counter becomes only able to increase at a rate of 10 increments of 100Q per second. The problem causes the rest of the game to slow down its visual processing, and some of the counters at the bottom of the main screen, as well as some text boxes, will be blacked out. This is not the only numeric problem: both Click Power and Girl Willpower can't be shown in measurements of anything above the trillions. It's gotten bad enough that in the Countryside, somewhere in the 4000s, their max WP starts showing up as negative, because the positive values don't go high enough. Aside from these issues, your game is operating well, and I'm quite entertained. Keep up the good work, as long as you're not sacrificing your health to do it.
Due to having access to YouTube, I've seen the Best Ending for Demon King Domination. It would be interesting to see if that little tidbit at the end (not stated here to avoid spoilers, but Changer knows which one, I'm sure) ended up tying into Heidal's presence in the Elf Kingdom, and why it was so easy for a weak Human to usurp the Throne. Heidal's policies made the Elves mostly horny sluts, and they no longer practiced combat in Coliseums, which is a great place to gain combat experience outside of war. This would also probably be a good subplot for Dianne, (if the player has summoned her by that point) because [spoiler alert] her kingdom was destroyed by the same entity, and she wants revenge.