Plastic pollution in the ocean has become one of the world's most urgent environmental problems. Footage of vast fields of floating plastic debris between California and Hawaii — now commonly known as the Great Pacific Garbage Patch — have driven home the gravity of the problem, with scientists and environmental groups warning that the colossal oceanic mess imperils the ecosystem and human health.

The issue is so pressing that it will be a key topic for discussion at the Group of 20 summit in Osaka in June.

And yet, the Japanese government has been reluctant to take strong legal measures seen in many other countries. At last year's G7 summit in Canada, Japan and the United States refused to sign the Ocean Plastics Charter that was endorsed by the other G7 members. The agreement would have committed Japan to the reuse, recycling, and collection of all plastic products by 2030. Tokyo insists it needs more time to assess the policy's economic impact.