The unidentified man's body was found yesterday evening in Hibiya park, which sits just next to the Imperial Palace in the heart of the country's administrative district, Jiji Press news agency and the Asahi newspaper said.
Tokyo police suspect that the man set himself on fire in the park, where he left letters protesting against Tokyo's endorsement of the right to exercise so-called "collective self-defence," the reports said.
In July, Japanese prime minister Shinzo Abe's cabinet announced it had loosened restrictions on the military in a highly controversial shift for the nation's post-World War II pacifist stance.
Ahead of that announcement, another man railed against the policy as he set himself ablaze on a pedestrian walkway in Shinjuku, one of Tokyo's busiest districts, while passers-by looked on in horror.
The bespectacled man, who appeared to be in his fifties or sixties, reportedly survived his apparent suicide attempt but authorities have not released details about his present condition.
Minor demonstrations have been carried out against the changes, mainly in Tokyo, often in connection with protests against restarting Japan's nuclear shuttered nuclear reactors following the Fukushima atomic crisis in 2011.
