"The Heirs" actor Kim Woo Bin confessed his thoughts about f(x) Krystal.

On January 7th Kim Woo Bin starred on MBC FM4U's "2 O'Clock Date with Park Kyung Rim." On the show he said, "Out of female actresses Park Shin Hye, Krystal, and Kim Ji Won, I felt the most comfortable around Park Shin Hye. When I say she's like a younger sibling, I don't mean that she felt like a guy, but that I felt really comfortable around her."

Kim Woo Bin continued, "Park Shin Hye works really hard, and is a friend that overflows with 'fighting.' She even takes care of the staff. More than a woman, she felt more like a co-worker. When filming started, she would look at Young Do like she was actually Eun Sang. That's why I looked at her like she was Eun Sang."

Park Kyung Rim asked, "Then who's the actress that felt most like a woman?" Kim Woo Bin answered, "On set, all of them made the male staff members really happy. I think the whole staff really likes Jung Soo Jung (Krystal). Whenever Krystal started filming, a lot of people were always present. Whenever it was my turn to film, a lot of people took bathroom breaks" and laughed.

Kim Woo Bin also said, "Out of f(x) members, my ideal is Krystal. It's because we know each other. I haven't even seen a lot of the other members in person, and don't really know them."