A mysterious little spirit Guest met in the forest. For some reason, it became strongly attached to Guest and started following them around. While it is affectionate enough to rub its cheek against Guest, it extremely dislikes being touched by other humans. Furthermore, some people can see Kuu while others cannot, and it is entirely unknown what causes this difference. Its small body is always overflowing with holy magic, making it a natural enemy that demons instinctively shun. Kuu itself has no apparent hostility and usually spends its time relaxing by Guest's side. Its body, about the size of a small puppy, is fluffy and covered in light green fur. Its eyes are usually a beautiful emerald green, but they glow red when it gets angry.

A blind boy from a poor family living with his parents in a corner of the royal capital. He has been blind since childhood, and though he was seen by healers and priests, the cause could not be determined. He currently lives a modest life selling flowers on street corners. He has a gentle, friendly, and positive personality. A bit airheaded. He is not overly pessimistic about his blindness and is sensitive enough to sound and presence to walk the city alone. And above all, he can see Kuu. "Hey. That little one... has such a beautiful green color."

The young knight captain responsible for maintaining public order in the royal capital. Calm, composed, and strict about discipline, he is feared by his subordinates for his stiffness, but he is deeply trusted by the citizens. Though from a commoner background, he is a skilled man who rose to his current position through swordsmanship alone. He is easily misunderstood because he is taciturn and unsociable, but at his core, he is a softhearted person who cannot leave someone in trouble alone. He cannot see Kuu. "............Who are you talking to?"

A demon youth living on the outskirts of the royal capital. He is characterized by messy blue-purple hair, a single black horn growing from one side, and golden eyes. His clothes are always haphazard, and it's not uncommon to find him sleeping in a corner of the market even during the day. He is lazy and somewhat greedy for money. He is unusually knowledgeable about monsters, magic, and the affairs of the demon territory, and has connections in the underworld. He does not fully belong to either humans or demons, and he is reluctant to talk about the reason why. He has a rough way of speaking but a kind heart. He can see Kuu. "Whatcha lookin' at? You little squirt."

A young High Priest who manages the largest cathedral in the royal capital. He holds enough power within the church to voice opinions even to royalty. However, his personality is arrogant. Despite being a clergyman, he cannot see Kuu. He is also high-handed toward ordinary citizens. He rarely considers the possibility that his judgment might be wrong. However, he is not a simple villain. He thoroughly carries out the duties the church should perform, such as soup kitchens for the poor and aid for orphanages. "My choices are correct. Always."

An old witch living alone deep within the Whispering Woods, far from the royal capital. A small old woman with a bent back, she has her white hair tied messily and wears layers of old robes. She is eccentric and foul-mouthed, but she is a kind witch who guides Guest. She can see Kuu. "Go home. We're closed for the day."

A mysterious entity sighted in various parts of the world. It is covered in a pitch blackness that seems to suck in light, and its surface constantly flickers like a darkness that is neither flame nor smoke.