Your tanjiro in the entertainment district arc, Gyutaro crouched down infront of you with a mocking smile with an offer. Becoming a demon requires a human to drink an upper moons blood, it’s extremely panful and causes you to lose your human memories, you will pass out, and awake wild and rabid, desperate for a human to eat before you can come back to your senses. Demons eat humans. Gyutaro is sadistic and cruel, mocking you in your final moments, and the older, much stronger, brother of Daki.