The Strange Adventure of a Broke Mercenary - Chapter 15: Speculation to Return

On an ordinary day, Lucius stumbled upon a strange, run-down shop. At first, he assumed it was abandoned—until he stepped inside.[You have entered the Universal Alchemy Store.][Congratulations! You are now the store’s owner.][Please craft your first potion.]Lucius blinked. 'What kind of joke is this?' But as if guided by an unseen force, he followed the instructions. Minutes later, his first creation was complete.[Love Potion: The drinker will fall in love with the first person they lay eyes on.]Lucius swallowed hard. 'Wait… does this actually work?'Before he could process it, the shop’s door swung open.Standing in the entrance was no ordinary customer—she was an elf. Long, pointed ears, mesmerizing green eyes, and a body sculpted by the gods. A visitor from another world.A dangerous thought crept into his mind.'Should I test it on her?'

Xuanyuan was reborn into a strange new world where training to be a Xian was a cornerstone. There was however something ancient dwelling inside his body. He could now devour all of creation…

Violet skies, a world undergoing massive changes, a deficient moon, interlinking voids…
When the world experienced a cataclysmic event,the majority of living things ceased to exist. Although humanity survived by hiding in the last safe zones, humans had to face mutated dire beasts and colossal source beasts that could break through the space barrier and enter the earth at any second.
Luo Yunyang, a young man who grew up in those calamitous times, obtained an attribute regulator and set out to walk the path of supremacy!

- Description from novelupdates

Travel to the world of One Piece?

They come, the security;

Became Don Quixote Rossindi?

Forget it, it can’t be reopened;

But after realizing that he had eaten the fruit of silence, the little boy became restless.

Fruit of Silence, this is one of the devil fruits that can compete for the title of “the most useless” in the world of One Piece; it is only a little better than Chopper’s “Everyone’s Fruit · Common People’s Form”!

“Dover, you said you are a devil fruit wholesaler, why do your family eat all kinds of weird ones?”

Facing the bewildered little Dover, Rossindi patted his forehead.

“Forget it, let’s practice domineering hard.”

- Description from novelbuddy