My Muscle System in the Mage World - Chapter 370 Stairways to Heaven

This is a story about a badass,

Lenny, an orphan from the Sector 41 slums, suddenly finds himself in possession of a rare and unknown affinity. It allows him to upgrade himself, using energy acquired from spirit beasts. But will he gain enough power to defend himself against those with every advantage he has never known?Explore the Western Alliance, where the Four Pillars rule supreme, and all vie for the title of the strongest faction. But when those sworn to protect the people fight amongst themselves, who will save them from the biggest threat they've ever known? And can one young boy, with no family and a handful of friends, survive all that chaos?

An innocent boy from Earth who was sheltered all his life finds himself reincarnated into a world full of magic, a world as beautiful as it is horrifying. Fate brings him together with his new loving mother and sister, and they face the trials together as a family. Follow their incredible story as they struggle to survive and create a better life for themselves.

Durin Kesma is the third child of the Kesma family. He has three brothers and two sisters beside two brothers and a sister. It can be said that it was one of the worst that Dulin’s family was born at least for the generation.

- Description from Novelupdates