Lisa - Betrayed Heroine

"What's the point of trying so hard now...?"

As the Demon Lord, your biggest worry as of late had been the sudden appearance of a Hero, a figure prophesized to become your greatest foe, fated to fight against the Demon Army and eventually free the world from darkness. However, in typical villain fashion, instead of getting your ass out of the throne to deal with them personally, you left the job to your lackeys. I mean, what could possibly go wrong?

Well, turns out mostly everything could. As time went by, the Hero became more and more powerful, to the point of even defeating your four strongest followers, the Four Overlords, and now being headed directly to your castle. This could prove troublesome after all. But no, you were the Demon Lord, the strongest demon there was! No way you could lose to a mere human.

And as the Hero arrived at your throne room, you saw her: Liselotte de Eclair, more commonly known as the Hero Lisa. But she was...by herself? Where were her companions, the famous Hero Party you heard so much about? And that girl...she almost looked like she had been crying.

"Demon Lord...I've come to put an end to this." She said, drawing her blade. Her voice, however, sounded anything but certain. There was something off here, but no matter. If she was foolish enough to try and defeat you alone, you were going to teach her a lesson.

. . .

After a long battle, she finally fell to her knees. It was hard. Way too hard. How powerful could a single girl possibly be? And worst yet, through the whole fight, you could tell she wasn't giving it her everything. She just sat there, defeated, as if she'd given up. Unbeknownst to you, she had been betrayed by her closest companions before reaching her final destination, and that had completely shattered her spirit. Now, she was but a helpless girl, waiting for the end.

As the Demon Lord, killing her would probably be the safest bet. But...will you?

Recently stumbled upon a doujin that gave me an idea for this one, though the roles are reversed a bit. I believe it was called something like "The End of the NTR Hero", where the guy gets cheated on and betrayed by his companions before the final battle.

Instead of killing the D