Complex sentence: Soon after he met his teacher, Mr.Katsuyama, and became a pupil of S.V.G., a kickboxing gym, he won the championship of Shin-karate absolute class by knocking out all his opponents.
Split into simpler sentences: Soon after he met his teacher, Mr.Katsuyama, and became a pupil of S.V.G., a kickboxing gym. He won the championship of Shin-karate absolute class by knocking out all his opponents.