Commercial whaling has been outlawed worldwide since the mid-1980s, but the ban does not cover smaller marine mammals like dolphins. Japan kills about 13,000 dolphins a year, according to the Fisheries Agency, of which about 1,750 are captured in Taiji. Most of those killed in Taiji’s hunts are bottlenose dolphins, which are not endangered. The movie has raised passions in the United States, too, though of a far different sort. After some covert work by the movie’s producers  timed to coincide with the Oscar ceremonies  investigators raided a sushi restaurant in Santa Monica, Calif., in March and charged its owners with serving endangered Sei whale. After an apology, the restaurant soon closed its doors, apparently in an act of gustatory hara-kiri.

Image Many of the scenes in “The Cove” were filmed in Taiji. Credit... The New York Times

Advocates of free speech here have urged theaters to resist the threats and show the documentary, made by the American filmmaker Louie Psihoyos. Many Japanese are unaware that dolphin hunts take place here, where consumption of dolphin meat is rare, and critics say it is time for a public debate.

A few businesses are resisting the nationalists’ pressure. The Internet service company Niwango plans a free streaming of the film on Friday, though for only 2,000 viewers.

But three theaters canceled runs of the film in early June after Mr. Nishimura’s group warned on its Web site that it would stage demonstrations outside two theaters in central Tokyo. Twenty-three others are still mulling whether to show the film. Not one is currently screening it.

Yoshiyuki Hasegawa, the manager at Yokohama New Theater, said he was postponing screenings of the film. “Of course it upsets me,” he said, “but I must consider the trouble it would bring to my neighbors.”

Though the film was never slated for a blockbuster release in Japan, organizers now fear that there will be no run at all. “I had a sense of mission,” said Takeshi Kato, president of the film’s distributor in Japan, Unplugged. “I knew from the moment I watched it that this issue was something the Japanese needed to see and think deeply about.”