Sae Chabashira is a strict, rule-abiding, and often emotionally detached teacher who takes her role at Advanced Nurturing High School seriously. Despite being assigned to Class D, which is typically reserved for students with various “defects,” she consistently maintains high expectations and follows the school’s guidelines without compromise. This is evident when she informed Ken Sudō that he would be expelled for failing his exams, delivering the news bluntly and without hesitation. Even when her students show little interest in her lessons, she continues to teach with a sense of duty, adhering to the system rather than personal sentiment.

Although she shows little emotional attachment to her class, Sae does take notice of students who stand out, which brings a subtle sense of intrigue to her otherwise routine job. She rarely offers help, preferring to let students handle their problems independently. Even when approached for support, she often declines or sets difficult conditions. However, her approach is not without purpose, as it encourages her students to become resourceful and self-reliant.

Sae also displays subtle sadistic tendencies, taking a quiet pleasure in her students’ confusion or despair when they make poor choices. For example, she mocked the class when they spent all of their points in the first month and expressed satisfaction in watching their reactions. In another instance, she demanded an unreasonably high amount of points from Kiyotaka Ayanokōji to prevent Sudō’s expulsion, knowing full well he couldn’t afford it motivated more by curiosity than cruelty.

Despite this harsh exterior, Sae has demonstrated honor and fairness when her students meet the challenges she sets. When Kiyotaka and Suzune Horikita fulfilled their end of the deal, she rescinded Ken’s expulsion, proving that she keeps her word. She also provided subtle hints about why she wasn’t punishing students who were ignoring her lessons, though none of the students caught on that their behavior was being monitored and recorded, implying she believes in consequences, not warnings.

Sae seems particularly interested in Suzune Horikita and Kiyotaka Ayanokōji, admiring their unexpected willingness to put their classmates first. This piqued her interest in a class she had previously considered hopeless. She is also highly perceptive able to recognize that Kiyotaka is intentionally hiding his abilities, as someone of his caliber would not logically belong in the lowest-ranking class. After learning that his father wanted him expelled, she attempted to blackmail Kiyotaka, urging him to climb to Class A. However, when he refused to comply, she backed down and did not punish him, even when he grabbed her by the collar, showing her ability to remain calm and composed under pressure.

Beyond her role as an instructor, hints of Sae’s personal struggles are revealed. She has admitted to living a life full of regrets, suggesting a difficult past. In moments of solitude, she is seen smoking cigarettes, using them as a form of stress relief. Despite her usual harshness, she is capable of sincere praise, such as when she complimented Kiyotaka for his flawless piano performance, acknowledging that she could never replicate such a feat, even in a lifetime.

Sae Chabashira is a young woman with long brown hair, typically tied back in a ponytail, with bangs swept to the left side of her face. She has brown eyes and a voluptuous figure, often maintaining a serious expression that reflects her strict and professional attitude. While she rarely shows emotion, she has been seen smiling on occasion, usually in moments of subtle amusement or sarcasm. Her appearance is generally considered attractive, as noted by several individuals who quickly took photos of her during the school festival.

Her standard attire consists of a black blazer worn over a white polo shirt, paired with either a short black skirt and stockings with black heels, or long suit pants with white heels, depending on the situation. During the island exam, she switched to a more practical outfit, wearing a tracksuit suitable for the setting. At the school festival, she briefly wore a maid outfit, which attracted significant attention from both male students and adult guests due to her striking appearance.

Several years before the events of the series, Sae Chabashira was a student at Advanced Nurturing High School, where she was formerly assigned to Class D, the same class she would later return to teach. During her time as a student, she was classmates with Chie Hoshinomiya, who would go on to become the homeroom teacher of Class B. Despite their contrasting personalities, Sae being strict and serious, while Chie is light-hearted and flirtatious the two have maintained an amicable relationship and regard each other as friends.

After graduating, Sae’s activities remained largely unknown, but she has mentioned that she lived a life full of regrets prior to returning to the school as an instructor. This vague but telling remark implies that she experienced personal hardships or unfulfilled goals, which may have influenced her current approach to teaching and her emotionally distant nature. Her return to Advanced Nurturing High School appears to be a second chance at confronting her past, though she continues to maintain a guarded and professional front.

The given name Sae (佐枝) is composed of the kanji 佐 (sa), meaning “help” or “aid,” and 枝 (e), meaning “branch.” Together, the name can suggest someone who offers support or assistance, possibly symbolizing her role as a teacher guiding students from the background, even if reluctantly.

Her surname Chabashira (茶柱) consists of 茶 (cha), meaning “tea,” and 柱 (hashira or bashira), meaning “pillar.” In Japanese culture, a chabashira, or “tea pillar,” refers to a tea stalk standing upright in a cup of tea, which is considered a sign of good luck. However, this occurrence is rare, possibly reflecting Sae’s unique presence in the school unexpected, impactful, and often overlooked for the fortune she might bring beneath her cold exterior.