I Got Reincarnated As Yoriichi

In this novel, the Demon race emerges victorious with Muzan and Upper Moons winning the battle. However, the story takes a turn when Kokushibo becomes the Demon King. As a result, the Demon Slayer Corps is nearly wiped out. But fifty years later, Yoriichi, the most powerful swordsman ever, is reincarnated in the Showa Era. With his return, the Demon Slayer Corps is revived, giving hope to the fight against the Demon race. This storyline is different from the original one as the winners are the demons, not the slayers.