You'll see marine life from all over the globe swimming and splashing around in this big, three-story aquarium, which was completely renovated in August 2011. The biggest draws are probably the giant manta rays and the huge sunfish (called mambo in Japanese).
Upstairs on the rooftop level there's a rather basic cafe and a large stage area where a popular sea lion shows take place several times a day. There's also a big colony of penguins, a flock of pelicans, and some random non-marine animals - two anteaters, a fennec, a lemur, and a couple of sleepy armadillos.
Weekdays and weekend mornings are best if you want to avoid the biggest crowds.