f(x)‘s Krystal gave her fans heart attacks when she unexpectedly released these sexy photos of herself wearing lingerie.

Krystal had never done such a revealing photo shoot before, so fans surprised to see her floating around in little more than a matching bra and underwear!

The photos were released in a photo book in 2017 as part of “I Don’t Wanna Love You”, a collaboration song Krystal made with Kim Joon Woon.