The trio of mathematics enthusiasts—Milka, Tetra, and their common love interest—is joined by a fourth member: Yuuri, a second-year middle school student and distant cousin of Milka's boyfriend. The bubbly young woman, who grows a taste for mathematical reasoning under the guidance of her beloved cousin, becomes dispirited after she learns of Milka and Tetra's feelings for her tutor. Determined to win over his heart, Yuuri immerses herself in the world of prime numbers, Pythagorean Primes, and Fermat's Last Theorem to impress him. As the four friends refine their understanding of the Taniyama-Shimura-Weil conjecture in hopes of understanding the solution to a jigsaw puzzle, tensions begin to rise. If they want to preserve the intellectual and emotional bond their shared love interest has carefully built with them, the three mathematical girls must sort out their feelings for him. [Written by MAL Rewrite]