Sawajima Yuichi—a time-traveling reporter working for Time Scoop Inc. Journeying through the ages, he gathers footage of people who didn't make it into the history books. This time his mission is to find yureki-sanka, people who traveled Japan teaching mathematics during the Edo period (1603-1868). They taught wasan—a distinct style of math that exploded in that era—to the common people. When a difficult problem was solved, the question and answer were written on a votive tablet and dedicated to a local shrine or temple. These tablets were known as sangaku. In the countryside of northern Japan, two mathematicians engage in a battle of wits, with the leadership of a village math school at stake. Watch as a thrilling sangaku challenge unfolds.