Typically observed from August 13th to 16th, Obon or (お盆) is a Buddhist holiday in Japan where it is believed that ones deceased ancestors come back to this world and visit their relatives.
The customs and the way that Obon is celebrated can vary from region to region, however the typical customs include hanging lanterns outside of homes to guide ones ancestors back into this world, otherwise known as "mukae-bon." "Bon Odori" or Bon dances are also performed at festivals in celebration of the holiday. One of the most common practices include families visiting the graves of their loved ones to clean them, pray and leave offerings of food.
Contrasting "mukae-bon," Obon is closed with "okuri-bon" where chochin-lanterns are used to guide the spirits back to their graves.
Festivals celebrating Obon occur all throughout Japan during these weeks, attending them can be a great way to immerse yourself in not only Japanese culture but the customs of the region you are in as well.
With Obon being a major holiday in Japan the mid-weeks of August can see peak domestic travel, with the worst days being August 11th to 13th.