|Yi Yon Su|
|Style||In Fighter (probably)|
|Wins by KO||9|
|Manga Debut||Round 376|
|Anime Debut||Round 19 (New Challenger)|
Yi Yon Su is a Korean Featherweight boxer who came to Japan and quickly raised his rank to the 5th position. He is the third boxer to challenge Makunouchi Ippo for the JBC Featherweight Championship. Their match was scheduled as the undercard to the WBC Middleweight title match between Bryan Hawk and Takamura Mamoru.
Not much is known about Yi Yon Su prior to the title match. He is presumably a strong fighter. However, he was knocked out in the first round by Makunouchi, who immediately used his signature Dempsey Roll. Yi was unable to track Makunouchi's movements and missed, while Makunouchi struck Yi across the chin. Yi was in a prime position for a counter, but the hit caused his legs to buckle. He was subsequently caught in the Dempsey Roll and a KO was declared without a count.
Yi Yon Su has fought 27 matches, 18 wins (9 KOs) and 9 losses after his fight with Makunouchi Ippo.
His appearance is similar to most Korean characters in the series so far, but mostly it is his hair-style of being rounded, this is the way Korean boxers had their hair in the past. Another boxer who is similar to him, is Li Chon Pir.
He doesn't really express himself much but before the match started, he looked confident and cocky just by looking at his smile.