Japan Railways (JR) operates a train from Osaka to Onomichi-eki every 5 minutes. Tickets cost $1 - $2 and the journey takes 3 min. 2 other operators also service this route.
How to get from Osaka to Onomichi-eki
From Osaka train to Shin-Osaka, train to Fukuyama, then train to Onomichi. 2 h ¥7201. From Osaka City Air Terminal bus to Kurashiki then train to Onomichi. 5 h 3 min ¥4768. From Osaka drive to Onomichi-eki. 3 h 2 min ¥3693.