In December, 2010, news about of the discovery of a special fish in Lake Saiko in Yamanashi Prefecture spread rapidly across Japan. It was the kunimasu, a relative of the sockeye salmon that was thought to have died out 70 years ago. But what's even more amazing, Lake Saiko was more than 500 kilometers away from where the kunimasu was previous known to live, Lake Tazawako in Akita Prefecture! How did the kunimasu reappear so far away? NHK joined forces with a Kyoto University research team using sonar and underwater cameras to observe the secrets of its habitat and how it survives. Tune into learn the amazing story of how the kunimasu was found 70 years after supposedly going extinct. We've also got rare footage of the kunimasu in the wild.