Ajisai at Sumida Park (墨田公園アジサイ) is very popular in June. There are about 7,000 Ajisai Trees in this park. In June, they will be blooming beautifully with rain. Ajisai, Hydrangea is the way to enjoy rainy season in Japan.
Tourist Info.
There is parking and restroom.
Access
0. At Asakusa Station.
1. walk (2 min.)
25 min
New Wave Samurai Movie. 
映画好き集まれ！ 
Sumida Park is located in the riverside of Sumida River at Asakusa, Tokyo. It is very popular for Sakura in April. Also, in early summer, Ajisai bloom beautifuly. In Fall, Higanbana, the spider lily will bloom and Plums in winter.
There are many sports facilities.
The most famous event at thsi park is the fireworks in the end of July.