The 17th of every month is regarded as the day of Kannon (Kuan Yin) Bodhisattva (Goddess of Mercy), and especially on September 17th called “Jūshichiya (the 17th night)”, various memorial services and events have been held at Sacred Sites of Kannon in various parts of Japan since ancient times.
Buddhist service is held from 18:00 on this day, at Nigatsu-dō as well. And from early in the morning until around 20:00, many votive lights are lit in main hall. In the evening, about 400 lanterns painted with wishes and drawings are placed around the main hall. 
From 18:30 to around 21:00, Bon-Odori Dance is also held in the square under Nigatsu-dō, and anyone can join dancing.