What was your childhood like?

I was born and raised in Muko City, a so-called “bedroom” suburb community in Kyoto Prefecture. My father was so fond of board games and puzzles that all sorts of playthings, such as Othello and backgammon (board games) and Rubik’s Cube, were everywhere in my home, with which I used to play almost everyday in my childhood. It was customary that I enjoyed board games together with my family members.

That said, I also liked playing outdoors as an elementary schoolboy. In my junior and senior high school days, I belonged to the Soccer Club. As for other types of pastime, I liked playing mahjong (Laughter).

We guess you were good at arithmetic since childhood, is that right?

I was good at arithmetic but not at calculation at all. Even today, calculation is my weak point. What I liked were puzzle-like problems and diagram-based problems like those often set in IQ tests.

I experienced a regretful setback when I was taking a test for admission to a junior high school. Despite months of hard work preparing for admission to Rakusei Junior/Senior High School, I struggled with one arithmetic question I simply couldn’t solve. So attached to that question, I had little time to review the other questions, which resulted in many calculation mistakes. Prior to that entrance exam, I had already passed the entrance exam for Todaiji Gakuen School, in which I was the only successful one among my friends who took the exam. This may have made me somewhat off guard. After all, my friends were admitted to Rakusei and I was the only one going to Todaiji Gakuen. Due to its unrestricted school culture, the Todaiji Gakuen School allowed me to study freely, which proved good for me as a result. Since that time, I’ve made it a rule to take other approaches and check my answers to math problems three to four times. The bitter experience in the junior high school entrance exam was a good lesson for me after all (Laughter).

About when did you make up your mind to focus on mathematics?

Toward the end of my high school second year, I was chosen as one of the twenty Japanese candidates for the International Mathematical Olympiad (IMO). This event turned out to be an opportunity for me to find fun in pure mathematics for the first time in my life. Joining the screening camp, I was surprised to find a number of extremely bright fellows who were as well versed in mathematics as being able to see through to the point of the problem. Until then, I had never met students of my age who were better at mathematics than myself, which was a tremendous stimulus.

At that time, I was left out of the final selection of six representatives to my regret. However, in the summer of my third year of high school, I had an opportunity to participate in a camp mostly for IMO representative candidates. It turned out that some of the fellow students I met there would change the course of my life. They invited me to go to the University of Tokyo to study mathematics together, so I decided to go to the university instead of the nearby Kyoto University. Then I was admitted to the university’s Natural Sciences I, left for Tokyo and began living there alone.

After entering the university, I seldom attended classes. Rather I made it a rule to attend a weekly reading circle with those friends after deciding which textbooks to read. In those days, I was desperately voracious for mathematical knowledge, spending quite some time to study.

Later, most of my friends in the reading circle chose careers as mathematics researchers. On the other hand, the six representatives, who actually took part in the Mathematical Olympiad, did not become mathematicians (Laughter).