Oriented in the same northwest to southeast direction as Hachijō-jima, the 1.3 × 3 km Hachijōkojima is surrounded by high cliffs.

Located in the Kuroshio Current, the area has abundant sea life, and is popular with sports fishermen and scuba divers.

During the Heian period, Minamoto no Tametomo was banished to Izu Ōshima after a failed rebellion, but per a semi-legendary story, escaped to Hachijōjima, where he attempted to establish an independent kingdom, and he built his castle on the more easily defended Hachijōkojima.

As the strait separating Hachijōkojima from Hachijōjima has a strong current preventing escape by raft or swimming, the more serious criminals were isolated on the island.

During this time, there were two hamlets on the island: Toriuchi (鳥打村, Toriuchi-mura) in the northeast, and Utsuki (宇津木村, Utsuki-mura) in the southwest.