Spring is the most awaited season in Japan simply because the blooming sakuras and other flowers are quite a lovely sight. Of course, most tourists prefer to see actual cherry blossoms and most will flock to Ueno or Meguro or Shinjuku Parks. Also, spring is a nice time to explore Tokyo because of the cool weather.
Luckily, we booked our trip a week ahead of the forecasted Sakura season in Tokyo. We arrived March 20 and we still got to see the 'early' bloomers in Chidorigafuchi Moat of the Imperial Garden and Ueno Park. Also, being early means less crowded parks.
Parks to visit during Sakura season:
Chidogarifuchi Moat at the other side of the Imperial Palace in Tokyo. During spring season, both locals and tourists flock here because of the scenic view of cherry blossoms surrounding the moat. Aside from that, there's also the East Gardens with lots of different hued sakuras and other flowering plants.
Chidogarifuchi Moat