Gu Jianhan is an orthodox cultivator (sword cultivator) who accidentally fell into the Taisho era.
It was discovered that the "ghosts" in this world are essentially "low-level evil cultivators" who are possessed by evil spirits and rely on devouring flesh and blood to survive, and the "breathing method" of the Demon Slayer Squad is just a superficial method of introducing air into the body. He does not have a Nichirin Sword, but uses his spiritual power to drive his natal flying sword to kill ghosts. While he was searching for a passage to the realm to return home, he taught the Demon Slayers the correct physical techniques...
Okay, come on, author