Seo Hye-rin, better known as Herin, was a trainee in SM Entertainment born on February 26, 2002 in Manchester, England, United Kingdom. She was member of a pre-debut training team SMROOKIES, she was introduced on July 8, 2015. In July 2017, Herin left SM Entertainment and joined the survival show Idol School, however, the company has yet to make an official statement about her leaving.