The fire of Infinite City burned away the countless sins of hundreds of years, and the Demon Slayer Corps finally gained a temporary break of sunlight in the world, but the darkness will never completely dissipate just because of the destruction of a ghost king. Ritsu Morikawa, a young Orion boy in the mountains of Kansai, was supposed to be guarding the wooden house passed down from his ancestors and living a miserable life of hunting and collecting herbs. However, a sudden mutant ghost attack tore apart his only stability, his parents. He and his young sister died tragically under the claws of demons. He was holding half a wooden sign with a strange cherry pattern engraved on it, and was rescued by a passing member of the Demon Slayer Corps' Anbu. With his body covered in scars and intractable obsessions, he became the most silent and marginalized member of the Anbu. He doesn't know the gorgeous breathing technique, and his hand that is used to holding a hunting knife can only play with herbs, repair equipment, and take care of logistics. His temper is as boring as an old stone in the mountains, but he remembers the pain of the death of his loved ones better than anyone else, and he knows better than anyone that there are still weird existences in the darkness that have not been cleared away. After the war, the Demon Slayer Corps was busy gathering the remnants, comforting the wounded, and destroying traces of ghosts. No one paid attention to the abnormal cherry-colored miasma that was gradually spreading in the mountains. No one cared about the mutant ghosts that were different from traditional cannibals and specialized in devouring the living. No one knew that the half wooden sign in Morikawa Ritsu's arms hid his never-known life experience, and was also connected to a forbidden secret land called the Forbidden Sakura Forest that had been sealed away by the Demon Slayer Corps for hundreds of years. On a mission to the mountains to recover the relics of old soldiers, he accidentally wandered into the edge of a miasma-filled cherry forest. He met Tanjiro Kamado and his entourage who had broken away from the main force to track down sporadic ghost traces, the taciturn boy Orion, and the gentle boy slayer of ghosts.
