One Piece: Kaido's Adopted Son, the Opening Eight Gates

Lin En starts off by traveling through the world of pirates. Good news: he obtains top-level domineering Haki at the start. Bad news: he is a baby!

Just when he was about to be bitten by the poisonous snake, Kaido fell from a high altitude to commit suicide and saved Lin En.

Lin En simply released his domineering Haki to attract Kaido's attention, joined the Beast Pirates, and was adopted as Kaido's son!

After surviving for 100 days, he obtained the Dragon Ball [Aerial Dance]. Lin En could fly without using the power of the fruit, shocking everyone in the Beast Pirates!

After surviving for one year, he obtained the Hokage's [Eight Gates of Ninjutsu], opened seven gates and repelled the Navy's Vice Admiral, shocking the Navy!

After surviving for three years, he obtained the [Magic Light Killing Cannon], and even the Four Emperors could not stop it with just one finger!

That's not all, there's also [Susanoo], [Chibaku Tensei], [Kamiu], [Teleport], and so on...

Kaido: "I have been sitting on the position of the Four Emperors for too long. It is boring. Im, please come down. I want to sit on the position of the King of the World with my adopted son Lin En!"