The 'Jung sisters', Jessica and Krystal, knocked fans over the head with their explosion of cute charms in a selca spree.

Jessica shared on her Weibo on the 2nd, "Rum pum pum pum, spending time with baby sis," and had some fun in front of the camera with Krystal.

Fans commented, "Jessica is being a good sister by promoting her sister's comeback," "How can they both be so beautiful," and "They are blessed, goddess-like sisters."

f(x) is currently getting fans to 'rum pum pum pum' for their 2nd full-length album 'Pink Tape'. 

It's hard to choose which photo is the cutest!