Complex sentence: Most of his instruction came from Takeno Takefumi and Chida Tsutomu, who he regards very highly and is repeatedly heard in seminars describing them as the best Aikido instructors on the planet that he has experienced.
Split into simpler sentences: Most of his instruction came from Takeno Takefumi and Chida Tsutomu, whom he regards very highly. He often describes them as the best Aikido instructors on the planet that he has experienced.