The Demon King Who Was Supposed to Lose Ended Up Defeating the Targets, and Now the Heroine Has Been Sent as a Sacrifice

The otome game “The Saintess and the Five Heroes” was one I played in my previous life, recommended by my sister. Essentially, it’s no different from a typical otome game. The heroine awakens to her powers as a saint, attends the same academy as the handsome targets, deepens her bonds with them, and ultimately finds love. There’s also an adventure part where they fight the Demon King, but it’s just an extra. You can achieve a happy ending without defeating the Demon King, and even if you choose to fight him, it’s designed to be easy with minimal leveling up. And then, I reincarnated as that Demon King. Considering the possibility that the heroine and the targets might come to defeat me, I decided to become strong enough to survive. But leveling up became so enjoyable that, before I knew it, my level had reached 999! By the time I realized it, it was too late. I had already defeated the heroine and the targets who came to fight me. Some time later, humanity, fearing they would be destroyed by me, sent the saintess—the heroine—as a sacrifice. What should I do!? How should I handle this!?