The idol group Keyakizaka46, a branch of Japan’s top-selling girl band AKB48, has sparked outrage on social media over their Halloween costume, which resembled the uniform worn by Nazi SS officers before and during World War II.

During a show Oct. 22 at Yokohama Arena titled “Perfect Halloween 2016,” the troupe, which ranges in age from girls of 15 to young women of 21, wore black one-piece dresses obviously inspired by military uniforms. Each one featured two rows of buttons on the abdomen, a cape and a peaked hat with a bird emblem that resembles the Nazi eagle. Many social media users criticized it as being “unacceptable,” with some posting pictures comparing the band with the Nazi Waffen-SS.

On Monday, Twitter user Takashi Sawanoi (@sawachan42) tweeted “(It’s) out!” while user @batayanF3 wrote: “Just because you didn’t know or because you don’t praise Nazis doesn’t mean you can do these kinds of things. It’s unforgivable considering how influential they are as talents.”

Formed in August 2015 by producer and lyricist Yasushi Akimoto, Keyakizaka46 is a group on the rise. They are a branch of the AKB48 tree, with their first single, “Silent Majority,” reaching No. 1 on the Oricon Daily Single CD Ranking as well as the Billboard Japan Top Singles Sales chart after selling roughly 260,000 copies within a week of its release April 6.

Also on Monday, Berlin-based Japanese writer Ichika Rokuso (@rokusouichika) posted a tweet that began: “Dear young people.”

“Seventy-one years have passed since the war ended, but there are still so many people who have lost their family members, friends and their loved ones. Even in Japan. You should understand that,” she wrote.

The costume also caught the attention of overseas tabloids such as the Daily Mail, which ran an article last Wednesday headlined “Japanese girl band cause outrage by dressing in Nazi-style outfits,” while the Daily Mirror ran a similar article last Tuesday.

In March 2011, Sony Music Artists apologized to the Simon Wiesenthal Center, a Jewish human rights nongovernmental organization headquartered in Los Angeles, on behalf of the members of the popular rock band Kishidan after it was claimed that a costume worn by the group during an appearance that February on MTV Japan resembled the SS uniform.

In an article published via Yahoo News on Monday, freelance journalist Rei Shiva worried that costumes considered culturally and politically inappropriate that are worn by Japanese performers could lead to a larger problem as the 2020 Tokyo Olympics draw near.

“Yasushi Akimoto, the producer of Keyakizaka46, is one of the members of the Olympic organizing committee executive board. While (Japan is) under the global media spotlight, it’s going to be terrible to be looking at productions and performances that cause international problems,” he wrote.

KEYWORDS WWII, AKB48, idol, Nazis, Keyakizaka46