Actress and film director Ku Hye-sun has been in a romantic relationship with actor Ahn Jae-hyeon, the darling of the mega-hit Korean rom-com series "My Love From the Star," Ahn's talent agency confirmed on Friday.

The top actress and the South Korean leading man started out as good colleagues while co-starring in KBS 2TV's fantasy-medical series "Blood" in 2015. Then, their relationship turned to romance, HB Entertainment said.

The two have been in a relationship for about a year, according to the agency.

In "Blood," Ku plays a surgeon whose uncle is a chairman of a conglomerate with medical subsidiaries. Ahn plays a genius surgeon who turns out to be a vampire.

Ku, 32, debuted in 2002 in a television commercial, and joined stardom through a number of hit shows, including MBC TV's sitcom "Nonstop" and KBS 2TV's romantic series "Boys Over Flowers." In 2008, the actress debuted as a film director.

Ahn, 29, has gained instant popularity for his supporting role in "My Love From the Star," playing the rebellious younger brother of the heroine, in 2014. The show was Ahn's debut on the small screen. His latest television appearances include entertainment show "New Journey to the West" on cable network tvN. (Yonhap)