Lin Yuan, an ordinary young man from the modern world, transmigrates by accident into the world of the Demon Slayer Corps during the Taisho era.
The moment he opens his eyes, he sees a snowfield stained red with blood and a figure he knows all too well: Kanae Kocho, the Flower Hashira of the Demon Slayer Corps, locked in a desperate battle with Upper Rank Two, Douma.
In the original story, she was supposed to die that night, leaving her younger sister with endless grief and regret.
But this time, Lin Yuan steps in front of her.
On the brink of death, a power unlike any other awakens within him: the Breath of the Sun, a legendary realm reached only by Yoriichi Tsugikuni, and the ultimate Breathing Style, combining the power of the sun with the fire of life.
As Douma's frost engulfs everything, a blazing sun rises in the night.
Every use of the Breath of the Sun burns away his life, and every act of salvation comes at a price. Kanae's survival changes the course of fate, but it also alerts the Demon King Muzan earlier than before. The fates of the nine Hashira are rewritten because of him, but new dangers arise as well:
The Upper Ranks gather, the Infinity Castle opens ahead of schedule, and the final battle is about to begin.
From a lone transmigrator to Kanae's devoted partner;
From a bystander who only wanted to change a tragedy to a warrior who truly protects this world;
From the first, tentative awakening of the sun to the ultimate awakening of the Amaterasu form.
Along the way, he'll fight shoulder to shoulder with the nine Hashira, battle the Upper Ranks to the death, and finally face Muzan Kibutsuji, lighting an undying sun for this world filled with tragedy.
