I Became the Main God's Lapdog at Super God Academy

Su Mu transmigrates into Demon Slayer before the story begins, becoming Tsugikuni Yoriichi. As in the original, he doesn't kill Muzan, and nothing major in the plot changes, except that he kills Tsugikuni Michikatsu. Then he transmigrates again, this time to Super God Academy, where he becomes a lackey of the main god.