The Miss Japan crown will remain unclaimed this year after its Ukraine-born winner relinquished the title over reports of an affair she had with a married doctor.

Karolina Shiino's nomination in January first sparked debate after some right-wingers questioned the Miss Japan title being awarded to a naturalised Japanese citizen.

Then a scandal erupted over her private life after the weekly Shukan Bunshun magazine reported on her extra-marital relationship -- a no-no for beauty pageant contestants, who are held to squeaky-clean moral standards.

Japanese entertainment personalities who have affairs, dabble in drugs or suffer other scandals also often find themselves shunned by their fans and employers.

The Miss Japan Association said it had accepted a request from Shiino to return the crown for "personal reasons", adding that there would be no Miss Japan for 2024.

Shiino said she wanted to "deeply apologise" to those involved, including the man's wife.

At first "I couldn't speak the truth due to chaos and fear... I apologise to those who believed in me and supported me," the 26-year-old said on Instagram on Tuesday.

"I take the situation seriously and have relinquished the Miss Japan Grand Prix title," wrote the Caucasian model, who moved to Japan at around the age of five.

Miss Japan, first held in 1950, is awarded for "Japanese-style beauty" consisting of "inner beauty, beauty in appearance and beauty of actions," its website says.

After the nomination attracted attention online, people continued to weigh in on the matter on social media.

"It doesn't matter if she is Jewish-Ukrainian or not, but I can't accept her character... Why is she Miss Japan?" one user wrote on X, formerly Twitter.

Others wrote in support of Shiino on her Instagram post.

"You have Japanese spirit. I don't think such (a) personal private thing should be a reason for you to step down but this is Japan," said a reply with nearly 350 likes.