Toshima-en fishing area
Located in Nerima, which can be accessed on the subway from Tokyo (either on the Fukutoshin line from Shibuya, or Oedo line from Shinjuku), has a very nice fishing area that caters to all levels.
The fishing area is more geared however toward those who want to leisurely fish on the weekend, or with their family, or who are inexperienced, etc. The area is a large open expanse of water that is maintained by the park moderators, and equipment and bait is all ready for you and actually included in the price!
The cost is 1,000 yen per hour, and is a highly recommended spot for some lighthearted and simple fishing on a nice day in Tokyo.
Here is the link (Japanese)