The Akinada Tobishima Kaido (安芸灘とびしま海道), also marketed as the 7 Bridges of Tobishima, is a 46-km road from Kure, Hiroshima across seven islands in the Seto Inland Sea.
"Akinada Tobishima Kaido" means "sea road of stepping stone islands in the Aki Strait", an apt description of this series of quiet road with seven bridges connecting seven islands to the mainland. It is also known as the Ura (Back/Rear) Shimanami Kaido after its neighbor, Japan's best-known cycling route, which passes nearby but is not directly linked.
There is essentially no public transport in the area: your choices are to drive or to bicycle.
The nearest train stations are at 🌍 Nigata (仁方駅) and 🌍 Aki-Kawajiri (安芸川尻駅), both on the JR Kure Line west of Kure and Hiroshima. Local bike rental companies like Kajigahama can arrange to drop off/pick up rental bicycles here, but by prior arrangement only.
The other option is to take a ferry in, either from Imabari, Ehime (Shikoku) to Okamura, or from Osakikamijima to Ocho on Osakishimojima. Since Imabari is a Shimanami Kaido terminus, there are many bike rental operations here and this lets you do the two routes back to back.
The main route is generally flat except for reasonable and well-graded approaches to the bridges. The first and largest bridge, Akinada Bridge, charges a toll for cars but is free for cyclists and pedestrians, while the remainder of the route is free for all.