Osaki-Kamijima one of the many islands of the Seto Inland Sea (Setouchi) only accessible by ferry. There are several ferry routes to the island, but I would suggest embarking at Takehara if you are coming by train. If you are already riding the Shimanami Kaido you can catch a short ferry ride from Omishima. There is also a ferry from one of the last islands of the Tobishima Kaido, a lesser known island hopping route in the Setouchi.
For cyclist, the route around the island is mostly flat with beautiful views of the surrounding islands and sea. It is about 20 miles around and with very little car traffic is an ideal place to take a ride. There are some beaches on the route, but the most impressive was the West side beach with the bay and island views.
There is a very nice hot spring with a view at the Kinoe Onsen Hotel Seifukan (きのえ温泉 ホテル清風館) and the picture below is from the Kannominesan Observation Deck (神峰山 第一展望台). You can see almost all of the Shimanami Kaido's islands from this point. The island life is quiet and the island isn't a tourist attraction just yet. Young locals are starting small businesses and organic farms. It is a unique island, definitely worth a visit to a truly Japanese place.
2020 New Years Day Sunrise