They use to relax, eat and drink and even sleep in parks under the blossom cherries trees. Those trees are sacred for them and the flowers are the symbol of purity.
I will let the images to speak.
Tourist also love the cherry blossom period. There are different species of trees and they blossom a very long period of time. The blossom wave starts in Tokyo an ends in Hiroshima. If you missed the festival in one place you can always go to the mountain villages and enjoy the flowers.
The japanese gardners use to cut the cherry trees brunches for them to be as long as possible and for the blossom to last as long as possible. They are masters in cutting trees.
You have to visit especialy the gardens of Japan. Those little spaces are very different from the parks. They are the climax of the japaneese skils in gardening. But that will be another story. _________________________________