One of the largest festivals in the Tohoku region of Japan, Hanagasa Odori Matsuri is held in Yamagata on August 5-7. Thousands of dancers holding hanagasa, which are hats made out of bamboo or rush and decorated with flowers, dance through the city while spectators cheer them on. The rhythmic pulse of the hanagasa songs keeps the dancers moving together as they march down the city streets yelling “Yassho! Makasho!” and twirling their hats to the left, right, up, and down.
Source: The Free Dictionary