Complex sentence: The organization was established on December 1939, with its leaders being Wataru Kaji, Yuki Ikeda, and another Japanese, a communist named Kazuo Aoyama, who ironically was on good terms with the Dai Li secret service.
Split into simpler sentences: The organization was established on December 1939, with its leader being Wataru Kaji. Other members included Yuki Ikeda, and another Japanese, a communist named Kazuo Aoyama, who ironically was on good terms with the Dai Li secret service.