Demon Slayer: I Control Muzan as a Doctor

I'm Fu Sha, and I've arrived in the Heian era of the Demon Slayer world! I'm the first demon in this world! And I'm a doctor, too! My current patient is named Ubuyashiki Tsukihiko! As a thoroughly good person, how could I let such a frail life slip away? So I squeezed a drop of blood from my heart and mixed it into a potion that could turn someone into a demon! But I left out one ingredient: the Blue Spider Lily! It's not that I didn't want to add it. The Blue Spider Lily is across the sea right now, so there's no way to get it. So you'll forgive me, Muzan… right?