Why Does Tanjiro Become A Demon Slayer?

A devil child who was raised by a devil hunter like a human child. Under the auspices of the devil hunter He finds love, affection, shelter, and knowledge without knowing his true self.

A 25 years old boy named John is suddenly shot by his friend, which results in his death, but is reincarnated again as the new Demon King. Unfortunately, he agains dies in a battle. This time also he is reincarnated but as a human. Follow Vis' adventure as he gets revenge, becomes a demon and makes his own harem.

He died killing the Demon King. He woke up sixty years too early. Now the monster is a young man. And he is running out of reasons to stay away. --- Lysan Dusk was the hero who saved humanity. He killed the Demon King, ended the war, and delivered the world from suffering, and his reward was betrayal. He wakes up in a young student's body in a dormitory room of a magical academy, and the calender shows that the date sixty years before he was born. The world outside hasn't broken yet. The war hasn't happened. Lysan's plan is to keep it that way by staying completely out of it. Fail his combat exams, spend whatever borrowed time he has left, living a quiet life, where nothing requires him to be a hero. The man who will become the Demon King, the most feared monster in history is still young and beautiful, with pale grey eyes that find Lysan across every crowded room like he is the only person worth seeing. Lysan knows what those eyes will become. He has looked into them across battlefields, spent a lifetime seeing them in nightmares. He never expected it to feel like this up close. Roman is everything Lysan was warned about — magnetic, dangerous, impossible to ignore. Everyone except Lysan, refuses to be charmed, refuses to feel anything at all. But now, he is failing spectacularly at them because Roman keeps finding him. Keeps watching him and making Lysan's carefully rebuilt walls feel like paper. Lysan knows the ending. But for the first time in two lifetimes, he is wondering if the ending can change. If the monster can be loved instead of killed. If staying is braver than running.

300 years ago, humankind created their own nightmare. Demons, are originally humans but the lust for power changed them inadequately, this is humans own doing. Around 300 years ago, a large asteroid bombarded the earth's very ground. This is the beginning of the birth of demons. This meteor was large, but out of the blue, a mysterious lifeform is intact in it's very core. A human named Cruzius Akiyoma was intrigued when witnessing these menacing looking creature. He interpret this as a blessing from heaven. He then owned the creature and conducted an experiment. He was surprised when he saw the structure and building blocks of life of this creature. He obsessedly pictured this as a one stepping stone through human evolution. He extracted the DNA of the creature and modified it in able to merged it to human DNA. Without any hesitation he then merged his DNA to the DNA of the creature. He is willing to offer his body to attain his goal, thus sacrificing his body is necessary. After the merging, he was surprised because nothing in particular happened. But, he suddenly felt a surging power circulating through his body. He screamed in pain as his body is gradually changing. Darkness fell upon humans as the scream of the first demon engulfed the sky, seas, forest, and fortress.

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Arianna had not planned on using magic to summon anything, she just wanted to get out of an arranged marriage. She was told of the ancient magic of summoning a guardian but instead she had summoned a demon—the demon king himself. But what would he ask in return for his loyalty to this princess?