Could The Hashira Turn Into Demons In Demon Slayer?

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.

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.

Miaka Von Speltsper, the myth, the legend and the daughter of two Gods. Miaka, the Demon King and the head of the Dark Council is the most powerful demon ever known to mankind, but she has a secret. She’s a hybrid. And the world she lives in has hunted down and eliminated every single hybrid in all the dimensions. But now…someone knows her secret, someone who has the power to destroy her. However, the world is changing and one of those changes is Kaleb Takeshi, the man with extraordinary eyes who has stolen Miaka’s heart with just one glance. But there is something about Kaleb that Miaka can sense but can’t describe. And not only is he human, he’s an enemy who has decided to give his loyalty to her. In this world of lies, deceit and betrayal; can Miaka trust her heart or will she have to choose century’s old traditions to stay alive? Because if she dies, it will truly be the end of the world.

When Mizuko slipped into the other world, she landed in the arms of a mischievous demon prince, Kenshi. New to the world, she didn't know he was a demon as he looked to her like he was a decent person. Because Kenshi helped her first, Mizuko decided to ask him for help in finding a way home while she fulfills the dead mage's request in relaying the message to the King. But no demon in Souzou helps unless they get something in exchange. A promise, it is what Kenshi wants the most.

Kiara was the Demon Queen And was ruling the Demon world, but suddenly an angel came to her world. He made emotionless Kiara believe in true love and then killed her brutally. However Kiara wanted her revenge. She was so desperate that her soul travelled in the time space, instead of dying. On the other hand after Kiara's death demon world destroyed, and Kiara's Crown which can give powers beyond their imagination fall in portal which connect all world together, That's why all the demons started searching for the crown. 10 thousands years later, (Human world) In hospital a girl with extraordinary facial features declared dead , but suddenly the girl opens her eyes and says "Prepare for destruction! DEMON QUEEN IS BACK. This time WHOLE UNIVERSE WILL SUFFER MY RAGE!"