Roppongi Sakurazaka may not be the biggest park in Japan, neither does it offer the biggest selection of sakura trees, but it does have 75 sakura trees and a few in the Mori Garden. It offers (at least at night) a decent chance to take some pictures of sakura trees with Tokyo Tower lit up in the background. Please note that you should definitely be using a fast wide-angle and tripod there.
Station : Roppongi (Hibiya Line)
Entrance Fees : Free
Opening hours : 07:00 to 23:00
Download your FREE copy via one of the following links :Tokyo No Sakura eBook