A mysterious doctor that works at the research facility that the boy and girl reside in. The boy assumes Doc is male, but isn't entirely sure due to his illness. Doc is deceptive, often lying to the boy whenever they have a conversation. He disguises himself to trick the boy, which is an easy task thanks to the boy's illness.

Spoiler

Doc works for a man he refers to as, "Senpai." His goal is to seemingly help the boy kill the girl, without the boy knowing that he's helping.