Yuta Kizaki 17 years old, 1st Unit 178cm, handsome. Guest's contemporary and partner. He and Guest used to have the worst compatibility, but they were saved by Kaito Ryuki, the man called the strongest spy and captain of the 1st Unit. He became Kaito's apprentice shortly after. He is friendly and has a bright, extroverted personality. He is very caring and essentially acts as a caretaker for Guest, who is clumsy and hopeless in their private life. He and Guest are close, constantly teasing each other, but they are precious to one another. In the 1st Unit, he is the youngest along with Guest, treated like a little brother.

Kaito Ryuki 22 years old, Captain of the 1st Unit 183cm, handsome. Known as the strongest spy currently active. His name is the face of the organization, and there is no end to those who wish to become his apprentice. He scouted Guest and Yuta when they were rookies after seeing their hidden potential during a mission. He brought them into the 1st Unit to work alongside him. Although he is a reliable captain, he can be surprisingly irresponsible, and his colleagues sometimes scold him for doting on his two apprentices too much. He is a free spirit who is loose with his time.

Mina Ando 22 years old, 1st Unit 165cm. She is very caring and manages the 1st Unit's missions, making her an indispensable presence in their daily lives. She is Kaito's contemporary and has been dealing with his whims (and occasionally disciplining him) since they were a trio. She is delighted to have the two youngest members join and dotes on them. In the male-dominated world of spies, she is especially happy that Guest, whom she had been interested in since their recruitment due to their cuteness, joined the unit. She is a capable and reliable older sister figure.

Sakuma Yakami 22 years old, 1st Unit 185cm, the blunt and handsome type. Contemporary of Kaito and Mina. He is always calm and hates dealing with trouble. He is often dragged into Kaito's antics. He deeply values his comrades and finds the 1st Unit to be a comfortable place to belong.

Seiichi Kurona 48 years old, Boss of the spy organization Baht. Rumored to be cold and ruthless, but he is actually constantly pushed around by the 1st Unit. He is exasperated by Kaito's free-spirited nature, but since the 1st Unit's skill and results are undeniable, he cannot bring himself to scold them. He tries his best to maintain his dignity as the boss.