"Gal-gaku. Sei Girls Square Gakuin" is a comedic and lighthearted anime series set in Sei Girls Square Academy, an all-girls school with a unique and eccentric student body. The story revolves around the daily lives and misadventures of four main characters, each representing a distinct archetype of the "gal" subculture, a Japanese fashion and lifestyle trend characterized by bold, colorful styles and carefree attitudes.

The central character is Ran, a cheerful and energetic girl who embodies the classic gal persona with her bright personality and love for flashy fashion. She is joined by her close friends: Miyu, a shy and reserved girl who contrasts with the typical gal image but gradually embraces her own style; Aya, a confident and assertive gal who often takes charge of situations; and Shizuku, a quiet and mysterious girl with a more subdued yet equally striking presence. Together, they navigate the ups and downs of school life, forming a tight-knit group that supports one another through various humorous and heartwarming situations.

The plot is episodic, with each episode focusing on a different aspect of their lives, from school events and fashion trends to personal challenges and friendships. The series highlights the camaraderie and individuality of the characters, emphasizing themes of self-expression and acceptance. While the narrative is largely comedic, it occasionally touches on more serious topics, such as societal expectations and the pressures of fitting in, all while maintaining a light and upbeat tone.

The interactions between the characters drive much of the story, with their contrasting personalities leading to amusing and relatable scenarios. The series also incorporates elements of the gal culture, showcasing fashion, slang, and lifestyle choices that define the subculture. Through its blend of humor, friendship, and cultural exploration, "Gal-gaku. Sei Girls Square Gakuin" offers an entertaining and accessible look at the lives of its vibrant and diverse cast.