Naruto: The Outsider's Resolve - Chapter 9.21 (336)

After an unexpected death, a soul finds itself reincarnated into the body of Itsuka Shido, an ordinary teenager in a world filled with powerful spirits, magic, and dangers from other dimensions. With the help of a mysterious system integrated into his body, Shido gains the ability to travel across worlds, summon legendary anime characters, and unlock a wide array of random skills and abilities.Disclaimer: The cover isn't mine, credits to the original artist.

The unparalleled Demon King Ye Xuan, who was able to heal the death or the living alike and holder of the medicine Holy Scripture, was betrayed and killed by his fellow Demon Kings. But he reincarnated into the body of Ye Xuan, the prodigal son of the Ye family and vowed to himself that he would return to his peak and take back everything that belonged to him!

- Description from Novelupdates

200 years after the world has ended, the laws of society have long been forgotten.

The Empire's forces retreated in desperation—trampled by faceless horrors bringing darkness and death to these once beautiful lands.Only the most courageous stood in defiance, forming a last defence to buy the people time to flee—fighting until the final embers of hope burned out.A man stands with a silver sword, like a beacon of hope to those around him. He roared with all his might drawing his blade against the overwhelming enemy!“You face Lancelot, Sword of the Empire! ”These horrors tested the Lord's grit and loyalty in the final moments.“Should my blade break, I will use my body!”The knights had fallen, broken swords for their tombstones, and lords fled, betraying the Empire to survive.“If my body breaks, I'll use my Soul!”Lancelot, the sword of the Empire, fought alone.All hope seemed lost.“And if my Soul fails...”What could a single man and his army do?He fights against the dark tide, blade in hand, heart on sleeve.“I will sell myself to the devil for revenge!”But he was too weak, too fragile.The last Lord of humanity stood against the enemy.Lancelot was a master of the sword, a mortal, neither a God nor a Saint.Miracles were beyond his reach.Now only a broken man impaled on his own destroyed throne.His blade shattered—now, like rose petals, it was scattered across the charred ground.Lancelot's soul was fated for the abyss as the light faded from his eyes.His last ounce of resistance used staring at the man who betrayed the Empire.Now with only the desire to kill, crush and seek revenge smouldering inside him.Now unwilling to die and desperate to fight once again.He desired to fight for the people who supported him.Lancelot refused to surrender, to fall like this.As quietly in the abyss, a voice whispered to him.It tried to entice the Lord, ignite his desire to win and fight again.“If given a second chance, to relive your life with a different choice... Would you Accept?”Blood gathered in his throat, forcing him to reply in his mind.A frail and broken voice'There is no reason to ask, of course!'“No matter the cost?”'Even if I were to lose everything...''If my people can live on. I would sacrifice everything I have!'“You will no longer be the same, a monster, twisted and vicious.”“Will you still accept?”The Lord's heart ached, taking great pride in his humanity.To lose that caused his mind to falter.Finally, out of power, unable to speak or reply with a trembling arm.Lancelot reached out.Towards the raspy voice.Towards the abyss.Towards a new future.[So you would accept after all...]'I must accept.''I must stand tall.''I must not break.''Because...''I am the Lord of humanity![Nay, you are the king of demons]