Probably you see a lot of these in Japan now.
These are for Tanabata – the Star Festival.
It’s based on a Chinese story.
One couple is separated by Milky Way and they are allowed to meet only once a year on July 7th.
We observe the day as star festival.
Usually we write our wish on a slip of paper and hang it on a bamboo branch.
There are kept for a while and burn at the end of the festival.
So if you are offered to write a wish, please go for it.