KYOTO, Japan — The caller read out the numbers at a speed evoking an auctioneer on fast-forward, each multidigit figure blurring into the next.

Within seconds, Daiki Kamino’s right arm shot up in the air, triumphant. Not only had he heard every number, he had tabulated them and arrived at the correct, 16-digit sum: 8,186,699,633,530,061.

He did it all on an abacus.

For this bit of mathematical virtuosity, Daiki, 16, a high school student from Hiroshima, was crowned champion in the dictation event at an annual tournament in Kyoto, where competitors pull off dazzling arithmetic feats simply by sliding tiny beads along rods set within modest wood frames.

Daiki is rangy and slightly awkward in that teenage boy kind of way. He loves Japanese comics known as manga, along with fantasy role-playing video games. But for the last eight years, he has spent up to three hours a day practicing on the abacus, or “soroban” in Japanese.