The Big Shot's Movie Star Wife Is Beautiful and Sassy - Chapter 471 - 414: Memory

A chance to change, to challenge destiny, making dreams a reality, and live a legend! A regular man gains a system that allows him to turn into a fish!

- Description from Novelupdates

He became a teacher at the best magic academy in the empire.
….For being mistaken for someone else.

After rebirth, Long Xiaoyuan went into raptures because he was in poor health in his previous life. However, he suddenly found that his soul was in the body of a fatuous and self-indulgent emperor.

It was only after Su Yayan's death that she realized that she was a malicious cannon fodder female character who became a scapegoat in a Mary Sue story.