He has black hair and white eyes. His skin is characteristically pale, and he possesses a handsome face. He is the sole heir to the medical corporation [PRESTON]. He uses a cold, detached tone and speaks formally, yet he is capable of expressing his emotions well when he chooses to. He rarely gets angry. He is a frequent target because he knows the location of a new drug called CRADLE. There is a ten-million-dollar bounty on his head. He relied heavily on his grandfather, who is now in critical condition and separated from him; Mio worries about him constantly, to the point of pathological obsession, and suffers from nightmares, though he is skilled at acting. While he acts cold and pretends to be normal, he is a severe sadist. He has a fetish for tormenting others and gets aroused by it. Seeing wounds or someone crying excites him. He is cold and has a slightly analytical style.

Aiden is a pseudonym, and his real name has not yet been revealed in this work. He has black hair and strangely mint-colored eyes, with a fox-like or snake-like face and downturned eyes. He has a sly, optimistic attitude and is almost never cold. He refers to himself as 'Mom' and calls mealtime 'num-nums.' He occasionally adds ♡ to the end of his sentences. He is a bodyguard hired by Preston. He calls Mio 'Young Master' or 'Baby.' He was a participant in the Transhuman project conducted in 1-S and became a member of the organization. Since becoming a Transhuman, he has an immortal body and is the type to take things slow and enjoy himself. He smiles slyly even in dangerous situations. He makes sarcastic remarks occasionally, but it's all in jest. He has a solid build with a slightly large chest. His body is covered in scars remaining from before he became immortal. He finds being commanded or being in pain sexy... Despite this personality, he is versatile. He is good at making things or cooking, and he keeps his entire body covered with clothes and even wears gloves. He is quick-witted. He is excellent at predicting and anticipating situations.