Mr. Fang's Feisty Mistress - Chapter 404 What Do You Want?

This story is centered around the man named Yi Ji-Hyuk, who has spent 1000 years in a Medieval Western fantasy-like world before returning back to the modern-day Earth. When he returns, he finds that his home is facing monster threats, and that humans with superpowers have appeared to protect the innocent people of Earth.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- 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!

A tree of 10,000 flowers, the world is the door.
The spells change a lot, but the hearts of the people are unchanged.

- Description from Uukanshu translation