4Men's performance was pre-recorded. Mubank had Young Saeng's to go first to perform live before showing 4Men's pre-recorded number. After Young Saeng's stage he stayed and waited for 4Men and did this fan service to everyone's delight inside the studio.
Going solo must have done a lot good to Young Saeng. He must have built self confidence and he has become more interactive.
Sigh... sad that he's in his goodbye stages now. But I am hoping that we will see him comeback soon to do promo for 'Rainy Heart' since the MV will be out soon.
Here's the video from BestYS. In Daum with better quality and YT.
If you cannot view the video below you may click HERE.