This is Fukagawa river (深川). If you want to see sakura without crowd or noise, this is the place.
Tourist info: Fukagawa is located in the Koto ward, Tokyo. Inside Fukagawa is a very famous Buddhism temple "Fukagawa Fudo-son." Many Japanese and foreigners visit the temple.
Fukagawa literally means "deep river," which is not exactly true for this river. Alongside of the river, there are many sakuras planted.
0. From Tokyo station.
1. use Marunouchi line (metro) to Ootemachi Station. (1 minute)
2. use Tozai line (metro) to Monzen-nakamachi Station. (6 minites)
3. walk north (10 minutes)