Despite its name, there are no monkeys on Sarushima, so you just have to bring your own. The only island in Tokyo Bay that does not have cliffs and beaches made of concrete, Monkey Island lies 1.7km off Yokosuka.
Covering a mere 5 hectares, the island controls the shipping lanes at the entrance to the bay and its strategic importance was recognized as far back as the mid-1800s. Military facilities that were constructed during the Tokugawa Shogunate remain today, including brick-lined tunnels and magazines where ferns now grow out of the walls.
The island's importance increased during World War II, and a series of connected artillery positions were sited on top of the cliffs at the northern tip of the island. All that remains now are the concrete bases embedded with rusting bolts, but the positions still command excellent views over the bay. Paths through stands of bamboo and heavy undergrowth take visitors the length of the island and up to the highest point–a mere 35 meters above the waves below where the paint on a three-storey lookout post is peeling.
At the most northerly point, a metal stairway descends the cliff face to a rocky promontory that is a favorite among fishermen. Clambering over the outcrops reveals rock pools and legions of shellfish, but the surfaces can be slippery and the tide can rise quickly, making getting back to dry land sometimes hazardous. A cave part-way down the face has a small statue with the familiar red bib surrounded by piles of small pebbles.
At the southern end of the island, looking across the water to the city of Yokosuka and the US naval base, the beach is a sheltered spot for swimming in the summer and barbecues for a greater part of the year.
According to legend, it was to this beach that a famous priest was guided by a white monkey, giving the island its name. The sand may be more grey and grainy than South Pacific fine, but it works just as well for sand castles and it may be the island's position in the currents feeding Tokyo Bay, but a lot of interesting flotsam seems to wash up on its shores. Dozens of different sea shells mark the high-tide line, along with pieces of wood rubbed smooth by the waves, the remains of small crabs, strands of seaweed and the occasional piece of colored sea glass.