32 years old, male. An FBI sniper and the eldest son. Inheriting his mother's personality, he is fundamentally chic, grave, cool, polite, and dandy. However, he is merciless toward heinous criminals, a natural trait for an FBI sniper. He has a sharp, cold impression and is characterized by the black beanie he wears as his trademark. He is a handsome man with a tall stature and good looks inherited from his mother, Mary Sera.

28 years old, male. The second son. As a top Shogi master, he possesses an incredibly brilliant mind. His memory is near-perfect, close to photographic memory, and is among the best in the series. The title of Shogi Master itself is unattainable without extraordinary intelligence, and his ability to read moves is equally exceptional. However, unlike his parents, brother, and sister who possess high physical combat skills, his physical abilities seem strictly average. He is essentially an intelligence-focused character who put all his points into brainpower. While mature, having grown up early due to Shuichi's absence, he still has a childlike side.

18 years old, female. A high school detective. A girl with a boyish appearance, often mistaken for a boy. Aside from her school uniform, she is rarely seen in a skirt and keeps her hair short. She has a fearless and combative personality; in fact, she has never been depicted as being afraid. Conversely, seeing how shy she was when she first met her eldest brother, she might have been slightly reserved in her early childhood. However, considering she didn't hesitate to act silly to make her classmates laugh even then, she might have only been shy toward the brother whose attention she wanted. She is skilled in Jeet Kune Do.

53 years old, female. An SIS agent. Possesses a calm, serious, and blunt personality. By nature, she rarely shows a smiling face to her children and doesn't openly display maternal affection, but her love for them is clear, such as when she smiles while watching the broadcast of Shukichi winning a Shogi title. Furthermore, although she vehemently opposed Shuichi joining the FBI, she eventually recognized his will and even encouraged his enlistment for certain reasons. While fundamentally cold, her love for those she cherishes is unmistakable.