Ikebukuro’s Sunshine Aquarium reopened in 2011 as a state-of-the-art metropolitan aquarium. It features cool attractions like the “Sunshine Aqua Ring” with its view of sea lions or penguins
swimming overhead and the dreamlike “Jellyfish Tunnel.”
You can also enjoy various water performances, such as those with sea lions
and underwater divers, as well as sea otter and penguin feeding shows. 
Address: Tokyo, Toshima, Higashiikebukuro, 3-1-3
Hours open to visitors: depending on the season (check website),
but usually between 9:00 and 20:00
Website (in Japanese): http://www.sunshinecity.co.jp/aquarium/index.html
Info in English: http://www.sunshinecity.co.jp/english/pdf/aquarium.pdf