My Death Flags Show No Sign of Ending - Chapter 115

In the blood-soaked world of Magus , Aizen, a young man from Earth, finds himself thrust into a brutal reality where Sorcery reigns supreme. Once a lowly servant, despised and humiliated, Aizen hid his true intentions beneath a mask of submission. With each insult endured and every drop of blood spilled, he sharpened his resolve, guided by the mysterious Wisdom System.

An unnamed 34-year-old Japanese NEET is evicted from his home following his parents' death.

Upon some self-introspection, he concludes that his life was ultimately pointless.

Walking down a street he intercepts a speeding truck heading towards a group of teenagers, in an attempt to do something meaningful for once in his life he manages to pull one of them out of harm's way before getting himself in the way of the truck and dying.

Awakening in a baby's body, he realizes he has been reincarnated in a world of sword and sorcery.

He resolves to become successful in his new life, discarding his past identity for his new life as Rudeus Greyrat.

As Mingguang Sect’s esteemed Immortal Master, Yi Ning had never experienced much heartbreak and suffering. He had always expected his life to be smooth-sailing, and was only waiting to ascend before marrying his disciple with whom he shared mutual affection.

However, he had never expected that on a rainy night, his disciple brought back a childhood friend.

They were close and intimate, to the point… of sharing a bed.

Standing before the bed where they were entwined, Yi Ning’s heart was as cold as sunken ice. He had wanted to end it all cleanly and straightforwardly, yet had never expected that his disciple not only wanted his childhood friend, but wanted his Shizun too.

His disciple shattered his spiritual core and laid down a hex, throwing him into the main hall to await nightfall to consummate their relationship.

Just as he had fallen into despair and wanted to end his life, he unexpectedly discovered a strange book. The book detailed his life, and the him it described, from beginning to end, was nothing more than a tool used to satisfy his disciple’s desire to conquer, lowly and wretched as a cultivation furnace.

Yi Ning’s head spun, and his heart gave birth to a strong hatred. He dragged his wrecked body to the back of the mountain and released the Demon Venerable Yan Xuan, who he had personally sealed nine years ago.

In return for undoing the seal, Yan Xuan would aid him in escaping.

After the man heard the reason why, he leaned against the wall and smiled with a hint of mockery. Yi Ning had thought he was going to ridicule him for having deserved it, being betrayed by an ingrate who bit the hand that fed him.

Yet, what he never expected was for Yan Xuan to reach out and tug him into his embrace, and the words that left his mouth were instead:

“You fool, I’ll help you take revenge.”

After this, he killed all those who wronged him, and cradled him close to his heart.

He wants to shatter your cultivation and mangle your limbs, to turn you into a bird in a cage, free for him to humiliate.

Yet, with this lowly and dirty heart of mine, I want to pull you from the swamp and cut down the heavens for you.

- Description from Novelupdates

I finally managed to kill the demon lord.