People from across Japan have been gathering in central Aichi Prefecture for some 2 decades to test themselves physically and mentally. The "100km Walking Challenge" takes participants an entire day and night to finish. Everyone has their own personal reason for signing up. One woman attends the event with her daughter, hoping to improve their relationship. One man decides to do the walk as a prayer for the safety of his estranged daughters. And an 80-year-old is participating because he wants to test his limits. What will they see beyond the finish line? We follow their two-day journey.