Demon Slayer, There's Something Wrong with My Moon Breath.

A half-complete Breath of the Moon, an alien soul who knows nothing about the plot, writes a legendary story. Many years later, Hei Death Mou shouted angrily at the young man holding the knife across from him with a broken look on his face: "You practiced wrong, your Moon Breathing breathing is not right." The silvery moonlight quietly brushed against Shang Xianyi's neck, and Tong Yexing chuckled at the severed head: "Senior Yan Sheng, what's wrong with my moon breathing?"