Sajangnimui Gonoe(2014)

Deputy manager Lee, who has been closeted for most of his career, attends a queer festival and accidentally bumps into his boss, revealing that he's gay. Although he thinks he's going to be fired, the boss coolly arranges a blind date with a man. The blind date falls through, but the boss wants Lee to meet his gay son, Do Won-U.

The boss plans to bring his son in as an intern, and Lee ends up becoming his mentor. But Lee doesn't like the the cocky Do Won-U, who uses his father's position to acts on his own terms...

(Source: KakaoPage, translated)