“Aki Monto” is a term for people living in Aki no Kuni (now part of Western Hiroshima Prefecture) who adhere to a Japanese branch of Buddhism called Jodo Shinshu. “Aki Monto” have a custom of decorating their family graves with special paper lanterns during the Bon Festival in summer. These colorful lanterns are unique to Hiroshima Prefecture.
In the animated film In This Corner of the World, you can see Suzu-san’s father holding just such a lantern.
Even today, many people in Hiroshima decorate their family graves with these colorful lanterns during the Bon Festival. However, on “hatsu-bon” (the first Bon Festival after death), mourners eschew these colorful lanterns, and instead use lanterns made only with white paper. At the end of WWII when many people in Hiroshima died from air raids, white lanterns filled Hiroshima’s graveyards.