The 5 whales shared this small pool for several years, before 2 things happened. The first was that Bubba, one of the whales from Oscar's pod, was sold to Ocean Park Hong Kong. The second, and much happier, was that Kamogawa Sea World built a new, larger tank. And, while the pool was still VERY small for the amount of whales kept there, with all the whales being so young, and considering the past facility, it was a huge improvement.
Oscar is one of Kamogawa's most agile whales. Still not a mature male, he is able to do some of the trickiest behaviors Kamogawa offers. Oscar fathered a calf with pod-mate Maggie in 1997, though the calf (a male) was stillborn, and Maggie died a few days later. Kamogawa Sea World had originally planned on selling Oscar, but has no decided against it, so he'll likely remain in Japan.