Harada Mutei, with a pen name AAA-Martin, is a tertiary character from Cell of Empireo, being mentioned in the DLC and having his first appearance in Hermit's Room. Mutei's occupation had been a doctor, writer, scholar, and an occult researcher. His known works are "Imagination Township" and "White Darkness," but a particular work the game brings up mostly is the "World Factor Theory," entailing that roles are determined and suggesting that humanity could manipulate their own reality akin to a God.

Mutei appears to be a mysterious, diligent person who had a fervent desire for knowledge, at the cost of his friends and family. In Hermit's Room, he expresses his regrets over "what happened," however it is difficult to discern whether this is to appeal to the Player or not.

According to Mutei, he driven his friend Langiri Utsugi "to insanity" and lamented over how Rumeld Othmayer was "right," as he went against a warning about experimenting on Theodore Riddle, which traumatized and incited the other, thus leading to the incident dubbed the "Chainsaw Incident."

It is heavily implied that Mutei's code was meant to be deleted, and any records of him are to be redacted and destroyed. However, the Player brings him back, providing their "colors," thus spawning him and the Hermit's Room into existence.