A member of AKB48 stirred up an online frenzy Thursday by getting a crew cut and posting an apology video for breaking the group's rule against romantic relationships.

The all-girl idol group, which has dominated the music charts for the past couple of years, maintains a self-imposed rule that forbids members from dating. But the weekly magazine Shukan Bunshun, which hit the stands Thursday, caught 20-year-old member Minami Minegishi coming out of actor-entertainer Alan Shirahama's house last month.

"What I did was imprudent," Minegishi said in a tearful YouTube video Thursday after her once-long hair was hastily shorn.

She begged for mercy from her fans and said she wanted to stay in the group, but acknowledged that her hair gesture "isn't enough to receive forgiveness."

The clip has already been viewed 4.3 million times.

AKB48 has seen members leave or be demoted as punishment for dating, and its managers said Minegishi, one of the founding members, will be demoted to "kenkyu-sei" (research) status, relegating her to an understudy or backup dancer role in the 88-member group, which comprises three main teams and a smattering of smaller units.

While the hair stunt had many questioning the act as well as the no-romance rule, Minegishi stressed that no one forced her to cut her hair off.

"I decided this all by myself and didn't consult anyone," she said.

Shirahama's agency released a statement Thursday saying the star's private life is his business.

AKB48 was formed in 2005 as the brainchild of media producer Yasushi Akimoto. It is known for its catchy pop songs and dance routines performed in school uniforms.