Father! Why are you doing this?!
The boy with tears asked his father, Muzan Kibutsuji who just killed everyone, his mother, his brothers and sisters. The boy Makoto Kibutsuji was shocked to see his usually gentle and benevolent father to suddenly killed his own father with sinister expression on his face.
Muzan left the house. Makoto succumbed to his wounds and took his last breath. Outside Muzan encountered the hashiras, the elites of demon slayer corps known for their role in hunting the demons.
All hashira used their special technique called breathing styles that allow them to imbued their weapons with supernatural power through breathing technique. It is only thing aside from wisteria and sunlight that can kill a demon.
But Muzan who was the demon king evaded all attacks and fought back the hashiras. None of the hashira could even scratch the demon king. The hashiras are all taken down by Muzan. Who decides to leave this place as soon as possible.
But Muzan has no idea that his action has given rise to a powerful enemy that could threaten the very existence of demon king and his minions.
******
A volatile power similar to Muzan's surged and preventing the death of Makoto, who somehow revived as his own demonic power awakens, becoming a human-demon hybrid. Makoto in his dream world recall everything that happened.
Suddenly he saw the vision appeared in front of him.
He saw a man in strange white dress, using blade on a uncouncious person.
But contrary to what he initially believed, what he shocked next shocked him, the man didn't simply cut the person, he checked the cause of what the person is suffering from, fixed it and knit his wound together.
Doctor Tsukishima, will he live?
The other people in white dress clapped as he done something good. The scene shift to different room, the person whose chest was opened and later closed, seems to be smiling and thanked the man, the person's family also thanked the man and praised him.
Suddenly a surge of images appeared in his head, it was memory of the man he saw. The man's name is Haruhiro Tsukishima. He is renowned doctor, good in many medical fields, he is good in surgery, made revolutionary medicines, created vaccines, have immense knowledge of diseases and disorders and how to cured them.
But that's not all, Haruhiro while a doctor, he is big fan of an comic series called demon slayer, which also had animated version. Haruhiro both read the comic and animation and he really enjoyed it. He was never bored of the story, the story is about a boy named Tanjiro Kamado looking for a cure for his sister, Nezuko Kamado, who was turned into a demon. For this reason he joined the demon slayer, to save humanity from demons, so other won't suffer the fate he faced, but also find a way to turn Nezuko back to human.
The villain is Muzan Kibutsuji, the king of demons, who was searching for a mystical flower called blue spider lily that could help him become immortal and allow him to walk under the sunlight, which is primary weakness of demon as a demon turn into ash after rays of sun fall on them. Muzan created many demons but giving a human his blood, turning the said human become his kin, his goal is simple to either find the flowers with the helkp of his minions or cosume one of his creation if he or she gain strength to survive the sun.
In demon slayers, the demons hunt humans as humans are nourishment for demon, often then hunting humans for their blood and flesh. Because of this demon slayer corps is formed to kill the demons to save humanity, they mastered breathing styles and wield nichirin blades to slay the demons. Tanjiro the hero of the story mastered hinokami kagura a ritual dance that can be used as breathing style. In a twist, the ritual dance turned out to be sun breathing, the original and most powerful breathing style from which all other breathing style came from.
Tanjiro, who managed to learn that hinokami kagura has unnecessary movements that make it different and weaker from sun breathing. He correct this flaws in final battle, allowing him to use sun breathing and slay muzan ending the war between demons and demon slayers.
Haruhiro, who was driving towards his home to rewatch his favourite anime, is hit by a truck. The truck's driver was drunk. leading to the truck colliding with Haruhiro's car, leading to an accident that took the life of renowned doctor.
******
Makoto finally woke up, his wounds are gone, he is alive and a realisation came to him.
Thanks to his past memories, Makoto got all answers to his questions about why his father killed the family and from whom he was running away from. Afterall, his father is a demon king, and his family was one of the fake family for Muzan to hide and after being found out by corps, he decided to eliminate his fake family as he has no further use of it. This revelation made Makoto's heart cold and he decides what he must do, to avenge his mother and siblings.