South Korea's Yu Myong-woo retained his World Boxing Assn. junior-flyweight title night by stopping Japan's Tomohiro Kiyuna in the 12th round of a scheduled 15-round bout at Inchon, South Korea.
Yu, 22, floored Kiyuna with a left to the jaw in the first round and again early in the 12th round before knocking him out at 1:53.
It was Yu's second title defense and 21st victory without a loss. Kiyuna, 24, fell to 15-2. Yu weighed 107 pounds, Kiyuna 108.