The cherry blossom season is still a full month away, but the early-blooming Kawazu-zakura type can be seen in a few spots around Tokyo. The flowers will last through the end of the month and possibly until the first week of March.
Here is where you can view them:
・The gardens in Hotel Chinzanso Tokyo (about 15 minute walk from Edogawabashi Station on the Metro Yurakucho Line)
Next to Aqua City Odaiba and along the shoreline
・Miura-kaigan Station on the Keikyu Line
While it takes a full hour from Tokyo (Take the Keikyu Train from Shinagawa Station), the area is home to about 1,000 Kawazu-zakura trees. Once outside the station, walk along the tracks in the direction of Misakiguchi (the direction opposite of Yokohama and Tokyo)