On an island off the coast of Ehime Prefecture, Fukushima Kazuhiko raises Bluefin Tuna, the "diamond of the sea." These farmed tuna, which he spends over four years raising, are sometimes even said to surpass wild tuna. They've overturned preconceptions about farmed tuna with their massive size, smooth fat, and refined flavor praised by the Toyosu Fish Market and by 3-star sushi restaurants. In 2020, Fukushima collapsed due to a stroke, and has had paralysis on his left side ever since. Despite being told a comeback was impossible, he returned to the sea, continuing to pursue his dream of raising "the best tuna in the world." We look at the devotion of a man who has banked his whole life on tuna.