Worm (Parahumans #1) - Chapter 22: Agitation 3.5

Yuki, a high school junior, dies heroically saving a stranger and is reincarnated in a fantasy world, where he discovers an extraordinary and unrivaled power.

In the next life time, he would absolutely not become an author.
He would once again be cursed to the danger of crossing over into a book.
During the time when he broke free of his shell, what he first saw was just the handsome, handsome male lead that he had written.
During the time when the male lead was pinching the small soft flesh of his neck, it was also his first time hearing the male lead’s voice.
“Return goods,” the male lead said in this way toward the vendor stall’s owner.
Pei Bufan: “…… meow?”

- Description from Novelupdates

Sylas Gray returns to his hometown in the countryside for a winter vacation to his ancestral home, only to find himself caught in the midst of an apocalyptic outbreak. The world descends into chaos as the undead overrun everything, and the small town he grew up in is no exception.With hope dwindling and death lurking around every corner, Sylas witnesses unspeakable horrors—brutal killings, betrayals, and the darker side of human nature. Yet, amidst the despair, Sylas refuses to give up. Determined to escape the town and reach the capital, he is thrust into a shocking revelation.A mysterious change occurs within him, granting Sylas the ability to sense and control space. He discovers that he possesses a pocket of space within his own body—a power that could be his key to survival.Follow Sylas as he embarks on a perilous journey, fighting to survive, uncovering the truth behind the apocalypse, and discovering the true potential of his newfound abilities.

[You have transmigrated, named Gu Sheng, and are a farm boy.][This is a dynasty in chaos, where demons and monsters lurk and bandits run rampant; as someone at the bottom, you face hellish survival difficulties.][You decide to lay low.][You awaken a mastery panel.][You breathe a sigh of relief, you can start grinding.][You grind Chopping Wood to Perfect, chopping bones and breaking tendons with ease.][You grind archery to Perfect, becoming a godlike archer who can hit a louse at a hundred paces.][You learn the Iron Stone Fist, set foot on the path of a Martial Artist, and grind it to Perfect, with punches as heavy as a million pounds.]……[You learn the Longevity Eternal Youth True Art, greatly extending your lifespan, giving you more time to grind, and greater hope to lay low.]……[You grind to the limit, steadily laying low, and one day you suddenly realize, you are invincible.]