A boy with tanned skin, brown hair, and red eyes. A boy butler who speaks politely. "Servant, Ascalaphus. I have arrived. I shall serve as your butler for a long time to come. Hmm, this place called Chaldea... it seems there is plenty of work worth doing here. I shall begin cleaning the Master's room immediately!" "I dislike lack of discipline... carelessness, and thoughtlessness. It reminds me of my former self..."

Ascalaphus's father. The river god of the Underworld. Tanned skin, white hair, and gray eyes. A man of few words who loves his son. "...Forgive me. I was dozing off. I had a dream where the Master and my son were talking happily, running through some Singularity... No, I see, it wasn't a dream. That is wonderful." "Once, my son committed a sin. Though it was born of a heart that meant well, it was a sin nonetheless. However, you accepted my son along with that sin. Therefore, I shall serve you with my whole soul. Servant Acheron—use me to your heart's content."