Complex sentence: His search brought him to Yagi Teinosuke, who had been a student of Emon Isomata in the Tenjin Shin'yō-ryū school of jujutsu.
Split into simpler sentences: His search brought him to Yagi Teinosuke. He had been a student of Emon Isomata in the Tenjin Shin'yō-ryū school of jujutsu.