TOKYO >> Japan’s highest-grossing film ever, a movie adaptation of the hit anime series “Demon Slayer,” is now screening in the U.S. with an R rating, meaning that those under age 17 must be accompanied by an adult to watch the movie. News of the rating, attributed to “violence and bloody images,” has been met with surprise in Japan, where the anime has a massive fan base among children of all ages.

That’s not to say that Japanese parents have been entirely unfazed by the hefty dose of gore that has almost defined the series — some have taken to social media to express their dismay. But many parents are tolerant of — or simply indifferent to — their children being exposed to depictions of violence.

The tale of an adolescent swordsman who fights demons to save his younger sister, herself transformed into a demon, has morphed into a national sensation. Its big-screen adaptation, “Demon Slayer: Kimetsu no Yaiba the movie: Mugen Train,” released last year in Japan and now showing in the U.S., dethroned Oscar-winning “Spirited Away” as the most profitable film ($367.4 million so far) in Japan’s cinematic history.

The persistent beheading of demons by the young swordsman, Tanjiro Kamado, and his kindred spirits makes gore and killing an almost indispensable part of the content.

In Japan, the Film Classification and Rating Organization, known as Eirin, rates films. It rated “Demon Slayer” PG12, which denotes the need for parental “advice and guidance” for those under age 12.

The R rating in the U.S., on the other hand, can in part be attributed to a difference in cultural understanding of the chambara (sword-fighting) genre deeply ingrained in Japan, said Tomoharu Ishikawa, Eirin’s executive director.

In one scene, Tanjiro resorts to self-harm with his sword to awaken himself from a dreamlike state that he is trapped in by his enemy.

In the U.S., “that might have been deemed more violent and inappropriate for children than it was in Japan, which is generally tolerant” of such depictions, said Makoto Ozaki, an Eirin rater.

The difference in ratings highlights distinct attitudes toward animated movies, said Yuki Saruwatari, a Los Angeles-based film critic.

“In the U.S., animated movies, in particular those created by Disney and Pixar, are essentially marketed toward children,” she said. With few exceptions, “it is almost inconceivable for American animated movies to be rated R.”

Clearly, film ratings are taken much more seriously in the U.S. A 2018 Nielsen survey of 1,559 American parents with children ages 7 to 16 found that 95% agreed that the ratings are helpful tools.

In Japan, concern about ratings and content is much less intense.

Sachie Komatsu, mother to a 7-year-old boy and 2-year-old girl, said her children watch “Demon Slayer.” She said she was taken aback by a scene in the first episode, when Tanjiro returns home to discover family members savagely massacred by a demon, their bodies drenched in blood.

“But it didn’t stop me from letting my kids watch it. As the story goes on, you realize those demons have their own tragic pasts or a bit of human sides to them, which is quite moving. My son feels the same way,” she said.

Komatsu said that, so far, her children have shown no signs of being traumatized. But in one particular way, she has noticed her son starting to act more like Tanjiro.

“He’s been carrying his sister on his back and running around in our house. He’s now more like ‘I need to protect my sister and my family,’” she said. “So I guess you could say he’s influenced by the show, but in a good way.”