The country's Fisheries Agency describes the mission as 'research for the purpose of studying the ecological system in the Antarctic Sea'

TOKYO, Japan – A Japanese whaling fleet returned to port Friday, March 31, after an annual Antarctic hunt that killed more than 300 of the mammals as Tokyo pursues the program in defiance of global criticism. The agency described the mission to kill the whales as "research for the purpose of studying the ecological system in the Antarctic Sea" in a press release. Tokyo’s claim that the annual expedition is undertaken for research purposes allows it to circumvent the International Whaling Commission’s 1986 ban on commercial hunting, to which Japan is a signatory. The International Court of Justice ruled in 2014 that Japan should halt Antarctic whaling and Japan suspended its hunt for one season to re-tool its whaling programme, including measures such as cutting the number of whales and species targeted. We will steadily continue our research toward a resumption of commercial whaling,” Fisheries Agency official Shigeto Hase said at a welcome ceremony in Shimonoseki, Yamaguchi Prefecture, home port for the fleet’s Nisshin Maru mother ship. “Each year that Japan persists with its discredited scientific whaling is another year where these wonderful animals are needlessly sacrificed,” Kitty Block, vice-president of Humane Society International, said in a statement. “It is an obscene cruelty in the name of science that must end.”

If the research excuse is bunk, why then do the Japanese keep hunting whales despite the international ban against it?
A Japanese fleet returns home after hunting 333 whales in the Antarctic. The Japanese government states that the purpose was for research.