The Seirei Waterfall with a height of 50 m is located in Otaki, Kamikawa-mura, Yoshino-gun, Nara Pref. The waterfall flows down the Otonashi River, which spring out of Aonegamine Peak rising 858 m above sea level, runs into the Yoshino River and then into the Kinogawa River, and finally empties into the Kii Channel. Legend has it that when Emperor Yuryaku (A.D. 418-479) enjoyed hunting in this mountain, a large horsefly came flying and bit him on the elbow. At this moment, however, a dragonfly appeared from nowhere and killed the horsefly, which the emperor greatly applauded and named the place “Akitsuno (the field of dragonflies).” As a rainbow is always over the waterfall due to the sun shining onto splashes of water, the area around the waterfall is also called “Nijikko (the rainbow light).” Being referred to in Manyoshu (Collection of Ten Thousand Leaves), the Seirei Waterfall is a scenic beauty with a long history.