The boss of a Japanese sushi chain bought a 467-pound bluefin tuna for $632,000 at an auction Thursday, and that’s not even the most he has ever paid. Kiyoshi Kimura, owner of Kiyomura Corp., bought the tasty fish at a price of $1,356 per pound, which works out to 74.2 million yen. Kiyoshi Kimura, center left,…