One Piece: I'm Destined to Be the Son-in-Law King! - Chapter 142: Ace Arrives

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

This novel is also known as A Stay-at-home Dad's Restaurant In An Alternate World

There is a very strange restaurant in the City of Sin.

Elves and dwarves must share a table, orcs are strangely well behaved, dragons are only welcomed on the small square in front of the restaurant, and the demons must bring their own stool.

This strange restaurant with their strange rules continuous to attract a long line of customers.

“This place serves the best food! The chef of this restaurant is a genius!” Some of the guests in the restaurant left glowing reviews. But these guests have a word of warning for other guests, “No matter what you do, never, never attempt to kidnap the boss or try to ‘eat and run’. You will die.”

A cute little girl stood near the door, and demanded in her tiny voice, “You have eaten the food, now pay up, or I will beat you to death.” The five-meter tall dragon suddenly felt a chill running up its spine.

- Description from novelupdates

Ajax used to coast through life before his parents died, after that he focused hard to try get his life back on track but that wasn't really happening and it all ended the day he got mugged. Given a second chance at life he now looks to become someone who matters and is willing to work hard from the beginning to make that happen.

After the college entrance exam, Su Mu, who comes from an ordinary family and works as a waiter in a hotel, accidentally breaks a priceless antique.The exorbitant compensation fee immediately sends Su Mu into a panic.With no other option, he reluctantly calls his father, Su Ruizhi, for help.Su Ruizhi said, “Son, don't panic. Let me tell you the truth. In fact, our family has assets worth billions, and even the luxury hotel where you work belongs to our family!”Ding! [Thirty million has been deposited into your bank account.]Looking at the bank notification on his phone, Su Mu is utterly dumbfounded.'Damn, I had no idea our family is so wealthy!'