Ring ni Kakero 1: Shadow-hen

After defeating Black Shaft's makeshift Team America, the Golden Japan Jr. team returns to training for the World Tournament that will be held in Tokyo. But during training the Shadow Clan, which uses boxing as an assasination technique, kidnaps Kiku in order to lure Ryuuji and the others into a fight to see who's truly the better representatives of Japan's junior boxers.
(Source: Anime News Network)