Japan's rainy season is famous for the beautiful hydrangeas that it brings, and there are more varieties than you can imagine!
If you want to appreciate the beauty of hydrangeas in all its splendor, then Kamakura is your destination! This hydrangea path in the Jojuin Temple (close to the famous Hasedera Temple) is definitely worth a visit, don't miss it!
Here you have a guide so some events (Japanese):
https://www.walkerplus.com/search/ajisai/