Duskbound - Chapter 26Book 2,

In this world, orphans or just anyone without any hope for this world can apply to become a “walking target”. Their sole purpose is to be a practicing dummy for the students of the sect who train to become “Demon Hunters”. These students need “walking targets” to test their training on living, walking beings of flesh and blood.
In exchange, they will be provided with food & shelter.
Their existence value is lower than a slave, but if they manage to survive a few years they can receive a life long pension.

Xiao Han is such a “walking target”. One time he witnessed a powerful Demon Hunter disposing a demon. When the demon died, a fragment of the demon that managed to escape entered Xiao Han’s heart. No one saw that, and even Xiao Han himself only felt some discomfort for an instant.

But that thing in his heart soon gave Xiao Han visions, and the first one is of a cultivation method which allows Xiao Han to absorb damage to enhance his body. A perfect cultivation method for a “walking target”.

- Description from Novelupdates

[Ding! Sorceress Beauty Merlin from Camelot has added you to a chat group full of beautiful maidens!][Ding! You've claimed the title of Supreme Demon Lord!][Ding! Fairy Queen Ophelia tagged you in a post!][Ding! Medusa sent you some of her spicy videos, shut your blinds before watching!][Ding! Your dog has been transformed into the Ancient Black Dragon Veligrpyh!]James Kang, once the youngest heir to the multi-trillion-dollar Hart Global Corporation, has everything anyone could dream of: money, luxury, and freedom. But his life is hollow—friends are fake, family distant, and his days are a blur of shallow extravagance.One late, lonely night, James gets a notification:[Congratulations! You have been added to the Ancient Multiverse Chatroom!]Thinking it's some cringy online role-playing game, he decides to entertain himself and plays along, proclaiming himself the “Supreme Demon Lord.”The group, filled with titles like:[Princess of the Azure Seas][Dragon Emperor of Ashvale][Goblin Slayer Supreme][High Priestess of the Sun][Fafnir, the Pet Wyvern]And they seemed hilariously invested in their roles.What starts as a joke takes a bizarre turn.The more James participates, the more he notices strange phenomena: glowing runes on his skin, magic artifacts materializing from nowhere, an elder dragon in his garage, and a sudden mastery of dark magic.Things escalate when a private group chat, run by a perverted female King Arthur, invites him to [The Table of Beauties], a circle of god-tier roleplayers… or so he thinks.Soon, James learns the truth.The chat is an interdimensional nexus connecting real worlds where magic, legends, and gods exist. His casual banter and fake roleplay have turned him into a living, breathing Demon Lord, complete with a castle in Hell, loyal monster armies, and reality-warping powers.To make matters even crazier, his “friends” start visiting Earth, and they’re nothing like he imagined!