“He called the square root sign the ‘temple of numbers.’ Inside the temple, numbers were protected, absolute, eternal.”
Chapter 1: The Professor
The story begins with the Housekeeper, a single mother, being assigned to care for the Professor, a brilliant but eccentric mathematician. Due to a traumatic brain injury, his memory lasts only 80 minutes. Despite this, he forms an immediate bond with the Housekeeper’s young son, whom he nicknames “Root” because of his flat, square-shaped head resembling the square root symbol (√). The Professor’s love for numbers and baseball becomes a bridge between them.
Chapter 2: The First Equation
The Housekeeper learns to navigate the Professor’s condition, writing notes to remind him of daily events. He teaches her and Root simple mathematical concepts, revealing the beauty in numbers. His passion for the game of baseball—especially the legendary player Enatsu—becomes a recurring topic, connecting his fragmented memories.
Chapter 3: The Birthday
The Housekeeper discovers that the Professor keeps old notebooks filled with mathematical proofs and clippings of baseball games. She learns more about his past, including his academic career before the accident. Root grows fond of the Professor, who treats him with kindness and intellectual curiosity, unlike other adults in his life.
Chapter 4: The Theorem
The Professor shares deeper mathematical insights, including the concept of “amicable numbers,” symbolizing friendship. The Housekeeper and Root begin to see the world through his eyes—finding patterns and meaning in numbers. Meanwhile, the Professor’s sister-in-law, who oversees his care, remains a distant but watchful presence.
Chapter 5: The Rainy Day
A rainy day keeps them indoors, and the Professor recounts memories of his past, though they fade quickly. The Housekeeper realizes that despite his memory loss, his emotions and instincts remain intact. Root develops a deeper appreciation for learning, inspired by the Professor’s enthusiasm.
Chapter 6: The Secret
The Housekeeper finds a letter in the Professor’s belongings, hinting at a tragic event in his past. She hesitates to ask him about it, fearing it may distress him. Meanwhile, Root prepares for a school math competition, encouraged by the Professor’s teachings.
Chapter 7: The Proof
The Professor helps Root with his math homework, and their bond strengthens. The Housekeeper reflects on how the Professor, despite his limitations, enriches their lives. She also learns more about his academic achievements before the accident, deepening her respect for him.
Chapter 8: The Game
Root participates in the math competition, and the Professor, though unable to attend, eagerly awaits the results. The Housekeeper sees how mathematics has given Root confidence. Later, she discovers more about the Professor’s past, including his love for a woman who may have been Root’s grandmother.
Chapter 9: The Farewell
The Professor’s health declines, and he is moved to a care facility. The Housekeeper and Root visit him regularly, but his memory worsens. Yet, in fleeting moments, he still recognizes them and recalls their shared love of numbers.
Chapter 10: The Legacy
Years later, Root, now a teenager, pursues mathematics in honor of the Professor. The Housekeeper reflects on how their time with him transformed their lives—teaching them about patience, beauty, and the invisible bonds that connect people beyond memory.
Key Ideas
- The fragility and persistence of human memory.
- The beauty of mathematics as a universal language.
- Unlikely friendships that transcend time and circumstance.
- The impact of kindness and intellectual curiosity.
- The invisible connections that shape our lives.
Who should read this book?
- Readers who enjoy quiet, introspective stories about human connections.
- Those fascinated by mathematics and its poetic beauty.
- Fans of Japanese literature and subtle, emotionally resonant narratives.