How Could I, as the Protagonist, Have a Bad Ending?

After traveling back in time to the protagonist of his favorite game in his previous life, Rean thought he could have a perfect ending like in the game. But looking at the villain who is about to rule the world, and the killer sent to hunt him down. Rean decided that he must achieve a perfect ending in this world. "I am the protagonist, how can I accept a bad ending?"