One Piece: Wudang Baiye, Deputy Captain of the Straw Hat Crew

A Wudang novice Taoist is brought to the world of One Piece by a mysterious book. He happens to meet Luffy just as Luffy sets sail, and is invited aboard.

In order to change this world, Baiye chooses to become Luffy’s vice-captain. During the Summit War, Baiye uses the true meaning of tai chi to command the Golden Light Spell and the Wind-After-Eight-Trigrams, the two supreme Daoist arts.

He becomes the number one celestial master in the world of One Piece. He even brings the Straw Hat crew onto the world’s top battlefield.

"Nami, come see the Clima-Tact I forged for you. Wind, rain, thunder, and lightning are all under your control."

"Zoro, come see the precious blade I forged for you. What a level, at minimum it’s a great blade."

"Sanji, why study the Marine Six Powers? Wouldn’t you rather learn my Wudang Cloud-Stepping Movement?"

...

The synopsis is weak, so please move on to the main text. It’s mainly about making up for regrets.