Angelina, whose real name is Hanako Hattori, is a prominent character introduced as an accountant from the financial department of the Kirishina Corporation. She is dispatched to the elite A-TEC class with a specific mission to slash their budget by seventy percent, a task she approaches with ruthless efficiency. Her presence initially marks her as an antagonist to the engineering students, as she scrutinizes their smallest procedures, from the disposal of old papers to their overall spending, and implements severe austerity measures that threaten the department's very existence.

In terms of personality, Angelina is known for being a no-holds-barred, grumpy, and hardline realist who is fiercely dedicated to her work. She is often described as vindictive and mean, with a tendency to dredge up sensitive information to get her way. A notable and recurring character flaw is her drinking problem; she is frequently seen consuming alcohol, which sometimes leads to complications, such as missing flights and requiring others to manage her responsibilities. She also has a persistent, unprofessional infatuation with her colleague Nagisa Kiryu, often making inappropriate advances toward him, which he consistently rebuffs. Despite this, her professional exterior occasionally cracks to reveal a more maternal side, and she is deeply invested in the success and safety of those she comes to care about. She is extremely sensitive about her real name, Hanako Hattori, and reacts with violent anger when others use it casually.

Angelina's motivations are closely tied to her professional role and her personal connections. Initially, she is driven by her assignment to cut costs and shut down the A-TEC class, acting as an agent of the corporation's financial restructuring. However, as the story progresses, her loyalties shift. Her primary motivation becomes protecting Nagisa Kiryu, for whom she holds strong personal feelings, and by extension, the A-TEC team he is involved with. She is not just a mindless corporate tool; she demonstrates a keen awareness of the political and financial machinations within the company, ultimately working to expose corruption and embezzlement rather than simply eliminating a department.

Within the story, Angelina plays a crucial dual role. She is initially the primary obstacle for the A-TEC team, but she quickly becomes a key player in their fight for survival. She serves as a source of critical information about the company's inner workings, revealing that the budget cuts were unknown to several top executives, hinting at a larger conspiracy. Later, she transforms into an active protector and combatant, using surprising physical skills to safeguard her colleagues. Her role expands from a pencil-pushing accountant to a field agent capable of handling violent crises, such as when she single-handedly subdues hijackers aboard a spaceship. In the series' climax, she takes a leading role in a mission to rescue Nagisa from a kidnapping and attempted murder by his own brother.

Angelina's key relationships define her character arc. Her relationship with Nagisa Kiryu is central; she is portrayed as his loyal colleague and self-appointed guardian, with an unrequited romantic interest in him. Her dynamic with Iris Shirasaki begins with professional distance but evolves into a camaraderie built on mutual respect after they face a life-threatening crisis together. She also has a significant, if initially adversarial, relationship with Kaito Sera, the passionate leader of A-TEC. While they clash over budgets and authority, they eventually come to work together, with Angelina showing a grudging respect for his dedication to his team.

Angelina undergoes a notable character development throughout the series. She is introduced as a one-note antagonist, a humorless accountant whose only purpose is to cut funding. As the series continues, layers of her personality are revealed. She transitions from being a mere extension of corporate will to a fully realized ally with her own moral compass. Her skills as a fighter emerge, and her motivations shift from pure professional duty to personal loyalty. The later episodes allow her to be a dramatic and emotionally separate cornerstone of the narrative, far removed from the early gags about her age and obsession with Nagisa. She proves to be more than just Nagisa's associate; she is a capable and decisive individual who takes charge when the situation demands it.

One of Angelina's most notable and unexpected abilities is her proficiency in combat. Despite her job in accounting, she is a highly skilled fighter, with her skills being described as those of a ninja. She is seen wielding a kunai, a traditional throwing knife, and using it with deadly accuracy against armed opponents. Her fighting style is effective and brutal, allowing her to take down multiple attackers in close quarters, as demonstrated during a spaceship hijacking where she disarms and defeats several terrorists. These "randomly ninja-like abilities" are a recurring element and provide some of the series' most well-animated action sequences, solidifying her role as the team's unexpected and formidable protector. Beyond combat, her professional abilities as a sharp, detail-oriented accountant are also a key asset, enabling her to uncover financial discrepancies that drive the plot forward.