Demon Slayer: Where Did Hei Shimou's Sword Come From?

[Black Death Mou solo + re-entering the wind + completing Breath of the Moon + plump character design] [A lot of original characters + Bu Dao original party + make up for some regrets] Yan Sheng accidentally traveled back to Iwakatsu Jiguo four hundred years ago, and after learning about his own strength, he planned to go back to the high road. The reason why I am one of the upper strings is because the highest string is one; No one can inherit the breath of the moon? Because as long as I am here, there is no need for inheritance; Kill your own offspring? I can't do this; I have been a ghost for a long time, and the world of ghosts is also very exciting. [Falling in love with Hei Shimo through a book]