f(x) and Rain got together for a short interview on yesterday's Music Bank, and it seems like they had some time to get to know each other backstage. Many of you should know that Rain's favourite girl group is f(x), and that he adores them. To show off his gentlemen side, he gave a signed copy of his new album, Back to the Basic, to the five girls. He left encouraging messages for each member, showing that he cares for them very much. After the group received the album, member Sulli went crazy, shrieking and jumping. The message that the world star left for her was, "To Sulli, I'm watching you." (may sound a bit awkward in English)  She showed off this message to her members and staff, and was very happy about it. She stated, "I'm so happy. A while ago, we were the ones to visit Rain-sunbae and gave him a copy of our album, but we didn't know he'll give such encouraging messages on his CD. We will work harder." The other members also said, "We are very thankful. We did not think that he would write messages for every one of us." It seemed like Rain's encouraging statements pumped up the girls, as they showed off a brilliant comeback performance!