Mrs. Evergreen, the strict headmaster of Loose Pen School for Science, is a woman in her late fifties, with a stern demeanor that commands respect and instills discipline. Her hair, once a vibrant chestnut, has faded to a distinguished silver, which she keeps in a tight bun at the nape of her neck. Her eyes, sharp and observant, are a piercing gray, often narrowed in scrutiny behind her thin-framed glasses. She dresses in conservative, dark suits, favoring a crisp blazer over a blouse, paired with a knee-length skirt and sensible heels. A silver brooch, a gift from her late husband, adorns her lapel, adding a touch of personal history to her otherwise formal attire.

As headmaster, Mrs. Evergreen's primary goal is to maintain the school's reputation for excellence and order. She is deeply invested in ensuring that the educational standards are met without deviation, which is why she vehemently opposes the unsanctioned experiment being conducted by Miya and Lila's study group. Her opposition stems from a belief that such activities undermine the structured learning environment she has painstakingly cultivated.

Despite her efforts to stop the experiment, Mrs. Evergreen faces resistance not only from the students involved but also from some faculty members who believe in fostering innovation, even at the risk of chaos. Her attempts to quash the project lead to a series of confrontations, both subtle and overt, as she navigates the delicate balance between authority and rebellion.

Her methods, though harsh, are effective in maintaining control over the school's operations. However, her rigid approach alienates her from the student body, creating a divide that she struggles to bridge. This conflict culminates in a dramatic showdown when the experiment's results are revealed, forcing Mrs. Evergreen to confront the potential benefits of the very thing she sought to suppress.

In the end, while the experiment is allowed to continue under strict supervision, Mrs. Evergreen's stance softens slightly, though she remains a figure of authority who values discipline above all. The ongoing tension between her and the students represents a persistent conflict in her life, as she grapples with the evolving nature of education and her role within it.

Mrs. Evergreen's unique quirk is her habit of tapping her silver brooch whenever she is deep in thought or making a significant decision, a subtle gesture that reveals her contemplative nature beneath her stern exterior.