Ember Dragon - Chapter 307: The Dragon’s Allies

It was the Great Age of Pirates, surging forward with their thousand sails unfurled.

One young man from earth ate the Goro Goro no Mi and joined the Marine.

Justice vs Evil, Freedom vs Tyranny, the colliding waves between them would never cease.

But all of this…..”I couldn’t care less about!!”

At the summit of the war, surrounded by ten thousand people, Ron held a thunder halberd in hand and walked forward with strong steps.

Rivals meet face to face, but only one could become the King.

- Description from Novelupdates

When 16-year-old Kyle Conner arrives at his aunt's for a holiday, he expects relaxation and freedom. Instead, his life is forever altered when he crosses paths with Lilith, the demon of lust and second-most powerful entity in the underworld.Forced into a dark pact, Kyle is transformed into a demon and gifted with a mysterious system that promises immense power. But this newfound strength comes with a deadly price: Kyle must hide his true nature and navigate the treacherous world of demons, all while being hunted by Lucifer and other malevolent forces.As Kyle struggles to control his newfound powers and unravel the secrets of the system, he discovers his ultimate goal: to overthrow Lucifer and bring about a new era of peace. But with the forces of darkness closing in, Kyle must confront the darkness within himself and make impossible choices to survive.Will Kyle be able to master his demonic powers, outwit his enemies, and fulfill his destiny? Or will the weight of his newfound responsibilities consume him, dooming humanity to eternal darkness?Note: this is a really interesting novel containing r-18 scenes, weaktostrong, overpowered, demons, systems, anti-hero...

In novels with a stud there is always a Senior Martial Brother like this:

In the early stages of the novel, his innate talent is high, his cultivation is good, his appearance is handsome, and he has an intelligent, cute younger Martial Sister as a fiancée.

In the middle stages of the novel, he is caught unprepared and defeated by a young disciple (the protagonist) in the sect who’s hardly remarkable at all. From then on, he falls from his godly altar and loses his brilliance. Even his young Martial Sister leaves him for someone else.

In the late stages of the novel, he continues to turn dark, going down the Demonic Path and becoming the major villainous boss. However, the protagonist still ruthlessly defeats him and his soul is eternally sealed.

Once Qin Mo opened his eyes, he discovered that he had become this Senior Martial Brother.

- Description from Novelupdates