Yook Sungjae (Hangul: ??ñ?ª; hanja: ‚??‘??‘; born May 2, 1995) is a South Korean idol, actor, singer, dancer and member of the South Korean boy group BtoB. He is currently signed to Cube Entertainment. He was a cast member in the variety show Real Men. He is best known for his supporting roles in Reply 1994 (2013) and leading roles in Plus Nine Boys (2014) and Who Are You: School 2015 (2015).