It's festival season in Japan. Sure, there are festivals all year, but around now they are rampant and you can be sure that there are some within a reasonable distance of you every weekend so you can take your pick. Of course, some places like this little Japanese-style bar have lanterns hanging year-round.
EDIT: And maybe a month after this photo was taken, the lanterns disappeared with the shop. Sadly, many businesses are being hit by the new, slightly more frugal Japan.