The first same-sex couple to dance at Vienna’s Opera Ball say they are continuing rather than destroying the event’s 200-year-old traditions, since they are “good dancers and stick to the dress code”.

Sophie Grau and Iris Klopfer, both students from Germany, have been accepted to join the procession of 288 young “debutantes” who will dance their first waltz at the Viennese society event on 20 February.

But the two school friends, who are not a couple off the dance floor, said they had applied for the event in order to challenge its conventions. “This isn’t about ideology,” Grau, 21, told news magazine Der Spiegel. “We just wanted to dance together.”

“It’s not really about gender,” said Klopfer, 22. “I have danced with a lot of men who weren’t very good at providing the lead. But with us the interplay of leading and following just works.”

Sophie Grau at an outfitter’s shop. Photograph: Dpa Picture Alliance/Alamy Stock Photo

The first Vienna Opera Ball to carry that name was held in the Austrian capital in January 1935, but the tradition of holding costumed dances during the Viennese carnival season goes back to the early 19th century.

This year’s ball, which has 5,150 registered guests and is expected to be watched live on TV by 2.5 million viewers, will be inspired by the Queen of the Night from Mozart’s opera The Magic Flute.

In order to be accepted for the event, Grau and Klopfer had to beat stiff competition for the limited number of debutante places, and assure a jury they were proficient at dancing the notoriously difficult left-turning waltz.

The pair will have to adhere to the Vienna Opera Ball’s strict dress code, with Klopfer wearing a white ballgown with elbow-length gloves and tiara and Grau donning a black tailcoat, white waistcoat, white gloves and white bow tie.

“The dress code makes sense to preserve the overall black-and-white picture on the stage,” said Grau, who identifies as non-binary. “During the ball I lean into masculine side. A couple who both want to wear the ballgown would probably have a harder time.”

Viennese high society has not greeted their imminent arrival with enthusiasm. Richard Lugner, an 87-year-old property magnate who each year pays a high-profile female celebrity to appear at his side, told the newspaper Kurier that dancing couples at the ball should consist of a man and a woman.

“If two women love each other, then that is accepted nowadays, but they have no business at the opening of the opera ball. Destroying the ball’s reputation should be avoided.”

Austrian businessman Richard Lugner presents a photo and a book of former ski star Lindsey Vonn. Photograph: Ronald Zak/AP

But the Vienna Opera Ball in its current form had already strayed from its traditions, Klopfer told Der Spiegel. “Traditionally the opera ball was about making your debut [in society] – and about marrying off your children. Luckily we no longer have that tradition today.”

The organisers of the event have defended their decision to accept the pair. “This is 2020; tradition does not exclude diversity and tolerance,” said Maria Grossbauer, who is organising the ball for the last time this year. “We support equal opportunities and oppose discrimination and homophobia, but we did not take the decision to provoke anyone.”

Real-estate tycoon Lugner, meanwhile, whose female guests at the ball have in the past included Sophia Loren, Geri Halliwell and Kim Kardashian, might this year have to turn up without a woman by his side.

At a press conference last Wednesday, Lugner announced former US skiing World Champion Lindsey Vonn as this year’s guest, holding up a picture of the athlete’s nude photo shoot to the cameras and listing the names of her former partners.

On Friday, Vonn announced on Twitter that she would not be attending the ball.