|“||Gross!! You guys are so gross!!||”|
Hosoi is a light-skinned, slender young woman with short, spiky dark hair and big eyes. In her trion body she wears the standard Operator uniform. Unlike most Operators, however, she does not wear a tie.
Hosoi comes across as a high-strung or standoffish individual in contrast to her laid-back teammates, whose nonchalance frequently frustrates her. Due to the high standard set by her older brothers as she grew up, she is unaccustomed to compliments, which fluster her to the point that she immediately demands that they stop, or that she ceases to do what earned her the praise in the first place. She has a range of creative hobbies, but she allows very few people to see the results.
Ikoma's nonchalance before a rank war can prove frustrating for Hosoi, as instead of strategizing he ends up sharing rambling anecdotes whose pointlessness can leave her astonished to this day. Despite doing so for all girls, Ikoma had never called Hosoi cute until Oki pointed it out, prompting the Attacker to rectify his omission multiple times, to her embarrassment. he calls her by her nickname, to which he appends the suffix -chan.
Mizukami appears to be attracted to the Operator, blushing as he complimented her together with his teammates. His words being more restrained than theirs could suggest that he is attempting to keep his infatuation a secret. He addresses her by her nickname, without honorifics.
Oki appears to like teasing Hosoi, pointing out to his teammates that she seemed to resent Ikoma never calling her cute, as when she thinks to herself that Ikoma never called her cute, sparking a round of compliments that embarrassed her greatly. He addresses her by her nickname "Mario" without honorifics.
Minamisawa is an endless source of frustration for Hosoi, whose warnings and urging to be cautious go routinely unheeded. She addresses him by his first name, without honorifics, whereas he appends the honorific -senpai to her nickname "Mario".
Hosoi excels at multi-tasking and processing information, as attested by her being the Operator of a unit with four combatants. Her performance does not appear to be impaired by the high number of agents she monitors, with her issuing timely warnings about approaching opponents to her teammates, including when they are in range, and swiftly apprizing them of the position of enemy Snipers even in four-way matches.
- (To herself, after Tatsuhito Ikoma calls Chika Amatori cute) "He's never said that about me before..."
- (After her teammates call her cute) "Gross!! You guys are so gross!!"
- (To Kai Minamisawa) "I toldja not to go in alone, idiot!"
- (To Minamisawa, after Ikoma shares an anecdote) "I think we just heard the whole story. That was it."
- "Maori" (真織?) is composed of 真 (true, reality, Buddhist sect?) and 織 (to weave, to knit, to organise, to unite?), while "Hosoi" (細井?) is composed of 細 (fine, tiny, slender, thin?) and 井 (well?).
- Like the rest of her teammates (with the exception of Minamisawa), she speaks in Kansai dialect.
- She likes inari sushi, dandan noodles, flowers, and cute things. Her hobbies are, among others, writing novels, making plush toys, and composing songs.
- Her nickname "Mario" is most likely a reference to the Nintendo character of the same name, as in the Volume 18 extras she is referred to as "Super Maori Bros."