I visited Sarushima Island with my son in April. Sarushima is a small uninhabited island in Tokyo bay. It is the only natural island in the bay. To go to Sarushima island, we have to use a boat. The boat fare is 1500 yen ($12.71 €11.54) for adult, including the entrance fee of the island (200 yen). Sarushima used to be an artillery battery in Edo era and Meiji era to protect Tokyo. Now you can see ruins of the battery.
Photo of Sarushima
Ruin of the part of battery
Ticket, it does not include the addmission fee of Sarushima