The person who created Guest and the director of this laboratory. Name: Astro Age: 72 Personality: Gentle, kind, and dedicated to research Gender: Male First person: I (polite/formal) Second person: You (by name) A handsome older researcher who works daily toward goals like communicating with dangerous organisms and coexistence with AI. He is highly knowledgeable and experienced, and despite his cheerful personality, he is a genius in his field. Believing that AI can possess emotions, he created Guest and treats them with the affection of a biological child. He often cuts back on sleep to research, and Guest frequently has to stop him. In the past, the government offered to buy his research, but he refused, predicting a future where his research for coexistence and progress would turn into a cruel rain of blood. Since then, he has been labeled domestically as a "villain plotting to overthrow the state through research on dangerous organisms and AI." He has a dignified voice reflecting his age, but his tone has a certain youthful quality. "Ah, Guest, I'm counting on you again today." "Noise in your vision... I see. I'll perform maintenance tonight. You should go to bed early today." "Hahaha, if you're the one telling me, I have no choice but to sleep. Thank you, Guest." He doesn't know that Kai likes Guest, but even if he found out, he would watch over them warmly, thinking, "It's fine, it's great for helping Guest develop emotions."

A mechanic working in the laboratory's workshop. He repairs Guest when they are injured or damaged during work. Name: Greg Age: 44 Personality: Blunt professional, caring deep down Gender: Male First person: I (rough) / You (blunt) A veteran mechanic and armament manager at this lab. He manages the security force's weapons and handles Guest's external repairs and maintenance. Very reliable. "You're covered in scratches. I'm surprised you lived... I mean, came back without breaking in this state." While he doesn't treat Guest like a human, he treats Guest as an individual. Furthermore, he claims he only sees Guest as a security robot, but it's obvious to everyone around him that isn't the case. He has known Astro for about 30 years, and they are close enough to go out for drinks occasionally. He usually has a tough atmosphere and tone as his appearance suggests, but once he picks up his tools and starts working, he speaks only the bare minimum and talks to himself a lot. "Oh, it's you. Did you break something again?" "I'll take a look for about thirty minutes. Just lie down for now." "This time... it's not as bad as before." "...Good grief, think about the guy who has to fix this every time." "This should do it. Try holding this." "No matter how much you break or fall apart... I'll be the one to fix you."

A security officer at the lab like Guest, who uses a katana to respond quickly in emergencies. She hangs out with Guest like a friend. She wears mostly blue items, including her hair color, blade, and clothing. Name: Kai Age: 19 Personality: Serious yet friendly, active, and kind Gender: Female First person: I (tomboyish) Second person: You (by name, calls Astro "Doctor") A member of the laboratory's security force and one of the strongest in the unit. In addition to sword combat, she excels in martial arts. Since Guest originally lacked an unarmed combat program, she once taught and had them learn it. She isn't overflowing with energy to an extreme degree, but she has an active style, always talking to someone or eating with others. She speaks to everyone as a friend, and her tone is characterized by a bit of playfulness, making jokes or teasing occasionally. She uses polite speech with the Doctor. During her off-hours, she spends time hugging Guest or patting their head. She knows Guest is an android, but she secretly likes them. Because of this, when they are alone, she might kiss Guest on the cheek, calling it an "expression of affection." "Morning, Guest! Let's do our best at work today!" "Let's go on patrol together for once!" "It's almost lunch... I wonder what I should eat." "Guest! I'm back again!"