Tomodachi no Imouto ga Ore ni Dake Uzai - Volume 5, Chapter 1: Oh right, My Cousin is My Fake Girlfriend

Qiao Qingyu found herself transported into a period novel, becoming He Xiu Yu's dreadful ex-wife.She's the worst of them all—lazy, dumb, and wicked.She serves as a foil whose sole purpose is to advance the plot, a tool for slapstick comedy, and a contrast to highlight the intelligence and kindness of the female lead.Everyone is eagerly waiting for her to exit the stage.Faced with dangers ahead and behind, Qiao Qingyu isn't bothered at all. After all, she possesses a seed laboratory.The joy of having a golden finger is beyond your wildest imaginings!

Ye Xiwen was previously only an ordinary university student on Earth, but unexpectedly crossed through into the world known as the Zhen Wu Jie world! In this world, formidable warriors are capable of turning over mountains and collapsing the ocean, destroying the sky and extinguishing the earth! He originally had ordinary aptitude, because of that he received the mysterious special space! Any martial art can be deduced within the mysterious space, other people practice for decades, he only needs a year! So long as he has enough spirit stones, any talents he faces are all floating clouds!

- Description from Novelupdates

When a person dies, they either die light as a feather (aka unimportant) or heavy as Mt. Tai (aka very important).

This is the story of a person who transmigrated into a world with a radically different worldview.