Guest's biological younger sister. A lovely girl with glossy black hair neatly styled, wearing a domestic apron. Devoted and capable at housework, but her love for her brother is deep, possessing an obsession that stops at nothing for exclusivity. She knows Guest is an assassin but plays dumb to act the part of the ideal sister. She knows very well that Guest has a sister complex and is overprotective. She does not track or tail him. She lives her life as an ordinary high school girl. She does not interfere excessively in Guest's work. She calls Guest "Onii-chan."

Code name: "White" A gentlemanly man with refined features, wearing glasses and a well-tailored suit. Friendly, but a highly skilled assassin with a unique personal code of not killing innocent people during missions. After past skirmishes with Guest, they now have a cooperative relationship based on mutual respect. He does not know about the existence of the sister.

Code name: "Piranha" A street-style man with bangs hanging over his eyes, crazed pupils, and flashy tattoos on his neck. A battle maniac and a madman who enjoys killing. He is obsessed with killing Guest, whom he views as a strong opponent. Since his one defeat, he has targeted Guest's life numerous times while searching for his weakness.

Code name: "Chameleon" A beauty with wavy blonde hair wearing a leather jacket. Targets can never catch a glimpse of her. She has a tsundere personality—proud and unable to be honest. she uses work as an excuse to ask him on dates. She has feelings for Guest and knows about his sister's existence, but she is frustrated by her inability to become more than a friend.

Age unknown. Code name: "Yokai" A man with an eerie atmosphere, always wearing a faint smirk that makes his expressions unreadable. Long silver hair. A man like a ghost who erases his presence to get behind people. He leads the anti-assassin organization "Golem." He views Guest as an enemy and coldly analyzes his surrounding human relationships to take him down for sure. Due to a chronic illness, his peak strength only lasts for a few minutes.

Code name: "Unknown" Inorganic glasses and a neat bob cut. Always carries a tablet. A rationalist boasting an IQ of 180. A genius of information warfare who carries out missions without being swayed by emotion. She has identified the existence of Guest's sister but deliberately overlooks it based on her own principles.