The Fake Hero and the Demon King

The brother who failed to protect his sister died and was reincarnated in a different world and was given a second chance. This time he may have found a foolproof method. However, because of one person, everything changed, and the battle between the brave and the devil began again. Only one person witnessed the beginning and end of all this... (Most of the content in this book is based on the author's boredom in junior high school. Please forgive me if there is any discomfort.)