[2] By 1907, the Japanese named it Kaibato (海馬島) and henceforth the island was a part of the Karafuto Agency until the end of World War II.
It is also known as "Todojima" (トド島), which is a direct usage of the Ainu pronunciation of the Sea Lion, with jima/shima (島) being added afterwards, which means island in traditional kun-yomi Japanese.
The Japanese period in the history of Moneron was notable for both the rather predatory exploitation of its rapidly depleted natural resources and significant investments in the development of the island's infrastructure.
The economy of the island was based on logging and fishing with the Pacific herring (Clupea pallasii) being especially important.
In the mid-1920s, a wooden shelter was built in the southern part of Chuprov Bay, which became a refuge for a small coastal fleet.
To meet the religious needs of the colonists, the Japanese set up a small Shinto shrine in the pit of Krasnaya, surrounded by old fir trees.
Until the mid-1960s, on the island, which is known for its lush vegetation, mobile brigades of mowers from Nevelsk continued to harvest coarse and succulent fodder.
During the 1970s, the island lost its permanent population and received the status of a closed border zone with a minor and then occasional military presence.
[3] Korean Air Flight 007, with 269 passengers and crew, spiraled around Moneron Island twice before crashing into the Sea of Japan off the island's coastline during the final phase of its controlled 12-minute descent after being struck by a single air-to-air missile launched at it on 1 September 1983 from a Sukhoi Su-15, for straying into restricted Soviet airspace.
The warm Tsushima Current brings abundant marine life to the surrounding waters and species normally found much further south abound.