One Piece: Fist of the World - Chapter 96: Nia vs. Tanaka

Should an untalented guy like me die?Then I’m going to die.I will die as you so desire.After dying, I will challenge the world again.Until I kill this tr*sh-like world!

As a cultivator, Lan Tian never expected she'd been hurled back to the 1970s countryside!Suddenly stripped of her powers, she's surrounded by mud - brick houses and farmland. Facing farming to social quirks with no modern conveniences, she relies on her cultivator's wisdom and resilience.

When crossing over to multiple books, Ren Shuhan found that every protagonist Shou was waiting for him to start chasing them in the crematorium.

“Don’t waste your time waiting,” He advised sincerely, “There are more 0s than 1s, so I’m not going to chase someone that is not interested.”

The protagonist Shou (sneering): Oh, there will be a day where you’ll lick the ground I walk on.

After waiting and waiting…

Ren Shuhan: “This is the wedding invitation for my childhood friend and I’s wedding.”

On the wedding night, Ren Shuhan removed the veil: “Baby, I’ve come to marry you.”

“Don’t you know that life is nothing but a play where you are the male lead and I am just a supporting character?”

“I know, but I don’t care.”

He was smiling, but Jiang Qingyue wept.

- Description from Novelupdates

The strongest Demon Lord dies, and reincarnates as a human. Not only that, he because of various incidents turns into the hero’s best friend.

Follow his journey as he tries to help the hero escape his fate, and on the sideline to conquer the continent while he’s at it.