Complex sentence: On April 1,1970, FM OSAKA started broadcasting as the first private FM station (second in FM) in Nakanoshima, Osaka nationwide as the only FM radio station affiliated with "Japan FM Network" (JFN) in the Kansai region.
Split into simpler sentences: On April 1,1970, FM OSAKA began broadcasting nationwide as the first private FM station (and the second FM station) in Nakanoshima, Osaka. It was the only FM radio station affiliated with the "Japan FM Network" (JFN) in the Kansai region.