Maybe a Fake Gintama - Chapter 596: When Girls Gather Together at a Party, Men Feel Like They’re Being Teased!

This is the story of a young slave gladiator in an underground arena. He doesn’t know about his past or how he got to where he is, only that his name is Aegir, and that he is strong.

A failed investor from 2017 got drunk and woke up in the 1980s. China is just opening up, and the economy is blooming. There is also the dissolution of the Soviet Union, the bursting of the Dot-com bubble and other financial crisis. He used his knowledge of the future and slowly build up his empire.

- Description from novelupdates

Su Bai wakes up and finds that the world has changed drastically. He realizes he has come to a world of pets. After accepting the new setting, he is determined to become a powerful Pet Tamer.