"Gakuen Utopia Manabi Straight!" is set in the near future, where Japan faces a declining birthrate, leading to a significant decrease in the student population. The story takes place at Seioh Private High School, a once-thriving institution now struggling with low enrollment. The narrative centers on Manami Amamiya, a cheerful and energetic transfer student who becomes the new student council president. Despite her lack of experience, Manami, nicknamed Manabi, is determined to revitalize the school and bring excitement back to student life.

Manabi forms a close-knit group with her classmates: Mei Etoh, a reserved and studious girl who initially doubts Manabi's unconventional methods; Mutsuki Uehara, a tomboyish and athletic student who often clashes with Manabi but gradually warms up to her; Mika Inamori, a shy and soft-spoken girl who admires Manabi's enthusiasm; and Momoha Odori, a mischievous and carefree student who adds humor to the group. Together, they navigate the challenges of student council duties, school events, and personal growth.

The series explores themes of friendship, perseverance, and the importance of cherishing the present. Manabi's infectious optimism inspires her peers to overcome their insecurities and work together to create memorable experiences. The story balances lighthearted moments with emotional depth, as the characters confront their fears and aspirations. Through their efforts, the group organizes events like the school festival and sports day, gradually rekindling a sense of community and pride in their school.

As the narrative progresses, the characters' relationships deepen, and they learn to appreciate each other's strengths and differences. The series concludes with a heartfelt graduation ceremony, emphasizing the fleeting nature of youth and the lasting impact of their shared experiences. "Gakuen Utopia Manabi Straight!" offers a heartfelt portrayal of adolescence, capturing the joys and challenges of high school life in a changing world.