Obon and tourou-nagashi / お盆と灯籠流し
In the film, there are several images of box-shaped paper lanterns. Some of them are white, and some of them are made of colored paper. Most of them have writing on them.
The lanterns are part of a custom in which those who have died are remembered. Their names are written on the lanterns, candles inside the lanterns are lit, and the lanterns themselves are set to float away on a river or stream symbolizing the transition of a life from this existence to another. Though the ceremony, tourou-nagashi, can be held at any time of year to commemorate lives lost, it is often the closing event of the Obon festival.
Obon is a Buddhist observance that usually takes place either in July or August depending on whether one follows the Gregorian or lunar calendar. Generally, Japan observes Obon in August.
While it is not a calendar holiday, many companies will give people time off around Obon so that they can return to their home towns. Most take time to visit the family grave, but customs vary from region to region. Generally, in addition to memorial services, there is some sort of festival held at the local temple at which foods like yakisoba and grilled corn are sold, game booths for things like ningyo-sukui (goldfish catching) are set up, and bon-odori (Obon folk dancing) is held.
Obon celebrates life as much as it honors the memories of those who have passed. It is a time for people to show their gratitude to those who have passed away, and it is a time to grieve over the losses of the past year, but it is also a time to think about how precious life is, and to remind ones self to treasure the bonds and friendships we share in this moment.