Kim Sun Ah gained 15 pounds to pay the role of pastry chef Kim Sam Soon in "My Lovely Kim Sam Soon." And still she looked great.

She slimmed down considerably to play the role of the celebrity shoe designer Hwang Ji An in "I Do I Do," looking fashionably slender in her designer clothes.

Her next role in the drama "Masked Investigator" will not require her to wear any designer clothes. In that drama she plays Yoo Min Hee, the tough-talking chief of a detective squad in a major crimes unit.

Yoo Min Hee is an elite graduate of the Korean National Police University. She is very is good at what she does but she also has a secret agenda.

The first on-set photo stills photos were released in the Korean media outlet Star Today and show the actress on location in Seoul's Hongdae area. The photos show that Kim Sun Ah looks effortlessly chic even when she is wearing a uniform.

Representatives of the drama's production company Kim Jong Hak Productions told Star Today that the actress has taken her role very seriously.

"While Kim Sun Ah is already well known for her ability to bring a character to life, we'd like to ask for much anticipation for what she will come up with this time, when playing her character Yoo Min Hee in 'Masked Investigator.'"

The role will be a small screen comeback for Kim Sun Ah, who has not done a k-drama since the 2012 "I Do I Do."

The 39-year-old actress did appear in a 2013 Chinese drama, titled "Competition of Roses," and played a woman driven to seek revenge in the film "The Five."

Her co-star Joo Sang Wook plays Ha Dae Chul, a prosecutor who is often frustrated with the justice system loopholes. Too many criminals escape for his liking so he comes up with an alternate identity that involves wearing a mask.

The two have a lot in common as they are both passionate about capturing criminals. But she does not know about his alternate identity and she would not approve. During the day he may cooperate with Yoo Min Hee to catch the criminals. But at night, when he is in costume, she does not make it easier for him. At one point she will discover his secret identity and he will uncover her secret agenda.

"Masked Investigator" is set to air on May 20 after the end of "Unkind Women."