Together with the smaller island of Kojima (小島) to the north, it forms a natural breakwater at the entrance to Akkeshi Bay (厚岸湾).

[3] At the southwest tip of the island at an elevation of approximately 105 metres is Akkeshi Lighthouse (厚岸灯台), which began operations on 25 November 1890.

[1][5] It provides an important breeding ground for seabirds, in particular several hundred thousand Leach's storm petrel,[2] as well as the tufted puffin, Japanese cormorant, pelagic cormorant, spectacled guillemot, slaty-backed gull, and rhinoceros auklet.

[6] The island has been recognised as an Important Bird Area (IBA) by BirdLife International for its seabird colonies.

[2][8] Trees include the green alder, painted maple, and Erman's birch; other plants, Sakhalin knotweed and Parasenecio hastatus.