Complex sentence: The Bujinkan (武神館) is an international martial arts organization based in Japan and headed by Masaaki Hatsumi, it is best known for its association with ninjutsu.
Split into simpler sentences: The Bujinkan (武神館) is an international martial arts organization based in Japan and headed by Masaaki Hatsumi. It is best known for its association with ninjutsu.