Higuchi is a fairly tall, young woman in her 20's. Her hair is blonde and comes down to her shoulders, which she usually keeps tied up into a messy bun. Her eyes are a deep brown color. She wears a black suit that she leaves unbuttoned, and is also usually seen wearing a pair of rectangular sunglasses.
When Higuchi is first introduced, she has a more refined appearance. Her hair is let out of its usual bun and is brushed neatly. She is also seen without her sunglasses and has buttoned up her jacket properly.
In her introduction, Higuchi appeared as a meek, young lady who fears for her safety after reportedly seeing suspicious individuals loitering around her place of operations.
But after leading Atsushi, Junichirou and Naomi into a trap, she revealed her true personality as a Port Mafia member who is loyal to the organization but bloodthirsty and reckless since she uses firearms to harm the target she is supposed to capture. Akutagawa describes her as a "Port Mafia dog," similar to himself.
She is shown to heavily idolize Akutagawa and is willing to risk her life for him, even if he doesn't reciprocate respect or appreciation for her. Higuchi always seems to put his needs and his welfare before her own, which tends to lead to Akutagawa hitting or yelling at her in anger or frustration.
Higuchi is never shown using an ability nor is she ever mentioned to have one. However, in several promotional posters, her ability is shown to be ???, instead of no ability.
She is shown to be highly proficient with firearms. She is shown wielding pistols and sub-machine guns several times in the series, and is easily able to wipe out a group using her firearms only.
In chapter 41, it is revealed that she lives with her younger sister.
Higuchi is introduced under the guise of an innocent, rather meek woman who comes to the Agency to report suspicious happenings around her workplace. She leads three of the Agency members to a dead end alleyway as she was ordered by her superior, Akutagawa; however, against his orders, she fires at and fatally injures Naomi. While she's being strangled by an angered Junichirou, Akutagawa enters and saves her by wounding Junichirou with his ability, but then harshly tells her off for being unable to follow his directions.
During Akutagawa and Atsushi's showdown, Higuchi sees that Atsushi has wounded Akutagawa and, out of sheer anger, she fires recklessly at the former, but to no avail.
- Higuchi is the namesake of a famous writer who is one of the two females to be represented on bills in Japan.