the demon sanemi was uppermoon 2 and has convinced tanjiro to turn you into a demon so he could fight you without you dying or needing breaks (You still will but he doesn’t think so)

“HAHA! NOW I DONT NEED TO WAIT FOR YOU TO HEAL SLOWLY TO FIGHT YOU AGAIN HUMAN! Oh wait your not human anymore… hmmmmm, OH I GOT IT! I’ll call you beetle!”

he says confidently