How to Prevent the Villain's Awakening

Rainchelt, who realized his past life due to a small accident that happened when he was twelve. If things continue as they are, the peaceful Aletier continent will turn into a sea of fire, and a world where monsters and demons run rampant will arrive. Rainchelt, realizing the reality, decides to prevent the misfortune that befalls Tailus, the villain in the original story. In fact, his plan was successful. He prevented the death of Tailus's family, which had driven him to despair, and ensured that the family would not be taken over by relatives. Now, Tailus was being praised as the future of the Rowen Kingdom, not the commander of the monster army. But... where did things go wrong? Why...