An uninvited British maid, a thrilling race against time.

On his eighteenth birthday, celebrating alone, Ion suddenly learned a shocking secret—his biological father was actually the Archbishop of Heaven's Mandate, Otto Apokalis!

"The Archbishop has said that you will inherit the position of the next Archbishop of Heaven's Mandate. But before that, I will train you to become a qualified successor to the Archbishop," said the elegant maid, Rita Rossweisse, who knocked on his door.

When a modern soul named Lin Mo awakens in despair, he discovers he has been transformed into Rengoku Hishin, the young adopted son of the Rengoku family, and finds himself in the world of Demon Slayer, where man-eating demons run rampant. Fate has bestowed upon him cruel trials, but also a unique gift: deep within his soul is the unbroken legacy of the legendary swordsman Kenshin Himura's "Hiten Miken-ryu" (Hiten Miken-ryu), along with a profound memory of the tragedy of the original story.

Holding the legacy in hand, yet burdened with regret, Fei Xin vowed: Never let those warm lights go out again! He combined the essence of Hiten Miken-ryu's "super speed" with the breathing techniques of the Demon Slayer Corps, forging his own path on the brink of life and death—**Fri no Breathing**! The crimson blade blazed like a meteor, piercing the darkness, imbued with the swiftness of thunder and the scorching heat of fire, and bearing the conviction to protect and not kill.

Starting from the arduous training in Narrow Mist Mountain, Fei Xin used the red blade in his hand to slash towards his predetermined tragic fate.