How to Live as a Tyrant's Big Brother

The day the empire collapsed due to rebellion and second-line erosion. The main character, Valen, dies with his sister, the emperor, and returns to 40 years ago. I will work hard in this life to prevent the destruction of the world and protect the emperor! So what I've chosen to do is living as a rascal more than one's previously If you were a jerk in your past life,