According to the American Interest article, Russia’s recent tough criticism of her ally North Korea might have to do with the discussion between Russia, Japan and South Korea over the construction of an undersea natural gas pipeline that will connect the three countries.
Map 1 Asia Pacific
North Korea is a communist country with very small production, while South Korea and Japan are capitalist countries with huge productions and huge energy needs. Japan is the 3rd largest economy in the world and South Korea is the 13th. Japan and South Korea have very hostile relations with North Korea, but the relations between Japan and South Korea are also very problematic. Japan invaded the Korean Peninsula and left only after the end of World War 2. The Japanese were cruel conquerors and exercised excessive violence against the Korean people.
However in December 2015 Japan and South Korea decided to leave their old differences aside and move on. See the Diplomat. This is very good for the United States, because these two countries are US allies against China in the South China Sea. But it is also very good for Russia because a common gas pipeline could be constructed in order to serve both countries. Currently these two countries buy expensive liquefied natural gas (LNG), mainly from Qatar and Australia. See Energy Information Administration below. Remember that Japan reduced her production of nuclear energy after the Fukushima nuclear disaster of 2011.
If this pipeline is finally constructed the Russians will be willing to return a part of the Kuril Islands to Japan. The Russians invaded the Kuril Islands after the end of World War 2, and these islands are the cause the Japanese and the Russians have never officially signed a peace treaty after the end of WW2.
Moreover, if a Russia-Japan-South Korea Pipeline was to be constructed, Russia could divert some of her gas exports to Europe towards East Asia, and therefore Russia could be willing to allow the European Union to reduce its energy dependence on Russia, which is actually the official policy of the European Union. Therefore even though an energy connection between Russian, Japan and South Korea would further complicate the geopolitical landscape, it could also relieve some of the tension between Russia and the European Union, since it would give Russia an alternative for her exports.
“Hoping to Please Japan, Russia Censures DPRK”, January 2016
“Russia proposes building natural gas pipeline to Japan –Nikkei”, October 2014
“Japan, South Korea Reach Agreement on ‘Comfort Women”, December 2015
Japan Energy Information Administration (EIA)