SEOUL, Dec. 27 -- Former K-pop idol Taeil, once part of SM Entertainment's boy band NCT, will remain in prison after South Korea's Supreme Court rejected his final appeal in a sexual assault case, according to Korea JoongAng Daily.

The country's top court yesterday upheld a lower court ruling that sentenced Taeil, along with two friends surnamed Lee and Hong, to three years and six months in jail for what is classified as "special quasi-rape" under the Act on Special Cases Concerning the Punishment of Sexual Crimes.

The charge applies when sexual assault is committed by two or more people, or against a victim unable to resist due to circumstances such as intoxication.

In addition to the prison term, all three men were ordered to comple...