The man, identified as 40-year-old Yasuo Yamamoto, turned himself in on Friday, confessing he flew the small drone to protest the Japanese government’s nuclear policy, according to NHK.
The aircraft was found to carry traces of radioactive substances. Yamamoto told officers that he had placed sand from Fukushima in a container attached to the drone.
The 2011 disaster at Japan’s Fukushima Daichii nuclear power plant, triggered by a massive tsunami, caused a meltdown of several of the plant's reactors and a leak of radioactive materials.
All of Japan’s nuclear plants were shut down following the incident and may only resume work if new and stricter safety standards are met.
Over the past year, Japan has moved toward returning to nuclear power, with several local courts approving the restart of nuclear reactors.