This Sword Cultivator is Somewhat Dependable - Chapter 547 - 44 "Know Yourself, Know Your Enemy

A young man who had longed for stories of good and evil since childhood lost his life in a tragic accident and was reincarnated as a boy named Chrono Mak in another world.

He learned that in this other world, there is magic and witchcraft, and depending on how you train them, you can become as strong as you want to be, so he decided to become the strongest demon king in order to recreate the story of justice and evil he once dreamed of.

In this story, a regular guy from our world becomes a young Main Branch heir of the powerful Hyuga clan in the Naruto world.He's primarily interested in gaining more power and doesn't care about right or wrong. He uses his knowledge from Earth and the Naruto show to get ahead, using his creativity and intellect to the utmost.As he tries to become more powerful, we see sides of the Hyuga clan and ninja world that weren't shown in the original Naruto story.He looks into the secrets of his ancestors, the Hyuga's eyes, and how ninja politics work, finding out things we never knew before and that the original author left unexplored.However, gradually, along the way, he also meets new lovers, friends, subordinates, and enemies and challenges how things are done in the ninja world - and also tries to unify it in the process and bring real peace around.

After his parents died, Alex Roth had a plan: become a wizard. Through hard work, he was accepted into the world’s greatest university of wizardry—but fate had another plan.

On his eighteenth, he is marked as one of his kingdom’s five Heroes, chosen to fight the land’s great enemy. But his brand is 'The Fool', worst of the marks.

Rather than die or serve the other Heroes like Fools in the past, he packs up his little sister, his childhood friend and her cerberus, then flees for the university in hope of refuge, magic and to unravel the truth about his land’s evil.

There’s one small problem: The Mark tries to ruin magic while enhancing skills outside of divinity, combat and spellcraft.…

…that is, unless he can learn to exploit the hell out of it.

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