The Hana Matsuri, a festival brought to the Okumikawa area during the end of Kamakura and Muromachi periods by warrior monks from Kumano and priests from Kagahakusan, takes place throughout the night, accompanied by chants of “teehohe, tehohe!" This event is a type of Shimotsuki Kagura used to invoke the rejuvenation of the sun's powers around the time of the winter solstice. This ritual performance has a history spanning more than 700 years and continues to take place today in the Tenryu River region.
The festival is thought to have originally centered on yutate  (the water-boiling ritual) and kiyome (purification), but it came to include elements borrowed from the Ise Kagura and Suwa Kagura as the locals expanded the festival, likely approaching its modern form about 400 years ago.
Back then, the festival was called Okagura, and it was a magnificent performance that consisted of 130 ritual dance sessions spanning 7 days and 7 nights. Due to its great scale, it required an enormous amount of money and effort, so 100 ryo of gold (about 3.75 kg in total) and 100 bales of white rice (about 6,000 kg in total) would be set aside, with more stored in Kagura-bayashi Forest in case that wasn't enough. People from several areas would get together every 7 or 20 years to hold this performance, but being such a major event, today's Hana Matsuri has been shortened, with the Okagura condensed into a one-day, one-night festival. Why the Okagura was renamed the Hana Matsuri is still a mystery, and there are ten or so different explanations regarding the origin of the name “Hana," which in Japanese is written with a character that means “flower".
The festival begins with the cleansing of the hanayado (ritual site), and continues around the clock with the kami-mukae (god-welcoming ritual); yutate (the water-boiling ritual); the myodo dance; the youth dance; the young children's dance; the oni (friendly Japanese ogre) dance ; divine blessings from the Negi (priest), Miko (shrine maidens) and Okina (old men) spirits; the boys' dance; yubayashi (the hot-water-cleansing ritual); and the kamigaeshi (god-returning ritual) with no breaks in between.
This festival, which includes the myriad spirit  summoning ritual, shoganjoju prayers (entreaties to the gods), the warding off of misfortune, and prayers for the rebirth purification ritual, was designated as a National Significant Intangible Folk Culture Asset in 1976, and it takes place with great fanfare every year from November to early March at 15 locations within the district.