Obon(お盆) is an annual Buddhist event for commemorating one’s ancestors. It is believed that each year during obon(10-15th of August), the ancestors’ spirits return to this world in order to visit their relatives.
Traditionally, lanterns are hung in front of houses to guide the ancestors’ spirits, obon dances (Bon Odori) are performed, graves are visited and food offerings are made at house altars and temples.
At the end of Obon, floating lanterns are put into rivers, lakes and seas in order to guide the spirits back into their world. The customs followed vary strongly from region to region.