Your Highness the Princess Depends on Me?

As a top assassin in my previous life, I was betrayed and killed by the most trusted organization... When he opened his eyes again, he was reborn into a world full of magic. In this life, he not only inherited all the memories of the previous life, but also gained extraordinary power. And I decided to live an ordinary life here... Right? Just kidding, who hasn't dreamed of being a hero? In his previous life, he was unable to carry out his own justice due to organizational reasons, so let's finish this regret in this life! Let's start by being an "ordinary" student! But things always seem to develop unexpectedly... During the day: My sister pushed me down on the bed and strangled my neck. "Are you saying that as a commoner, the first princess of the royal family has agreed to your confession?" "Yes, I promise that was the first time we spoke!" "What about the second princess?" "The second princess seems to have relied on me because of my bravery..." "... Do you think your sister is easy to deceive?!" "Sister! Don't do anything yet... Listen carefully first!!" Evening: I turned into an invincible passer-by "Dare to kill the leader at the headquarters! The organization has surrounded this place! You have nowhere to escape!" After hearing this, I threw my head up and laughed "Hahahahahaha" "Escape?" "Who's trying to escape?" "Why run away!!!" As the last words were shouted, the magic power soaring into the sky surrounded the entire kingdom. The besieging people put down their weapons in despair, "Who are you?" "Me? I'm just a passer-by."