I attended a "hanami" or flower viewing, in a much less popular area than Tokyo in early April. The Kawaguchi area of Saitama is definitely a hidden gem. The spot I traveled to, about a 40-minute bus ride from Ikebukuro Station, is very close to the Arakawa, a river which is lined by sakura trees.
The hanami had about 40-50 people gathered to enjoy the blossoms, food, drinks and live music, even in unseasonably cold temperatures. This area seems to be a lot less crowded during hanami or "flower viewing" season, as it is just outside Tokyo. It may be a nice spot to ditch the crowds but still view sakura along the river.
