Chizuru Tachibana is the principal of Mihama Academy, a position she holds due to her personal connection with the institution and its most notable student, Yuuji Kazami. Coming from a prominent family as the only daughter of a prefectural governor, her life took a significant turn following a terrorist attack at Vancouver Airport. During the hostage crisis, Chizuru was taken captive by a gang member. Due to her small stature and youthful clothing, she was mistakenly assumed to be a middle school student. She was rescued by Yuuji Kazami, who successfully shot the man holding her hostage. In the chaotic aftermath, as she was nearly taken captive again, an operative named Daniel Bone knocked both her and the assailant into the sea. After the rescue, the team was surprised to learn she was actually older than both Yuuji and Daniel. Profoundly grateful for her life being saved, Chizuru was insistent on repaying her debt to Yuuji. When he expressed a desire to experience a normal school life, she eventually fulfilled this wish by granting him enrollment into Mihama Academy.

In terms of appearance, despite being around thirty years old, Chizuru has a remarkably youthful look, often being mistaken for a student or even a junior high school girl due to her short stature and childish figure. She is very conscious of her age and appearance. Her typical attire includes a brown long-sleeved jacket worn over a white blouse, paired with a short black skirt and black heels. She often styles her hair in two bunches with bangs framing her face, and prior to her role as principal, she wore her hair down and donned round-framed glasses.

Her personality is a blend of professionalism and mild-mannered grace, which allows her to command respect from colleagues and students despite her youthful looks. While she usually maintains a composed exterior, she is frequently the victim of Yuuji’s teasing, which tends to make her snappish around him. However, when the situation calls for it, such as when dealing with serious matters regarding the school or student welfare, she reveals a more mature and serious side. A notable quirk is her habit of speaking very quickly when she is telling a lie.

Chizuru’s primary motivation stems from her feeling of obligation towards Yuuji. She is willing to bend rules and leverage her position to assist him, providing him with classified information or requested items like vaccinations. Her role in the story is largely that of an ally and benefactor to Yuuji, having offered him the opportunity for a normal school life that he sought. She oversees Mihama Academy, where the main narrative unfolds.

Regarding key relationships, her bond with Yuuji is central. Beyond her gratitude, it is hinted that she harbors deeper romantic feelings for him, viewing him as her prince who rescued her from the hostage crisis. In a later story, her jealousy is shown when she reacts by banging her head on a wall upon seeing Yuuji marry someone else. Despite these feelings, she remains supportive of him regardless of his romantic choices. Her interactions with Yuuji are also marked by his fondness for teasing her, leading to her frequent exasperation.

In terms of development, while she is a consistent supporting figure throughout the series, deeper glimpses into her personal sentiments reveal a character who balances professional duty with genuine, personal affection for the protagonist. Her physical abilities are largely unremarkable, but she notably cannot swim, a fact that was discovered during the hostage rescue incident. She does, however, possess a keen ability to manipulate systems behind the scenes due to her status as the principal and her family background as the governor's daughter, allowing her to secure resources and information that would otherwise be inaccessible.