F(x) made their first appearance as a 4-member group at the recently-concluded 2015 London Korean Festival.
Krystal, Luna, Amber, and Victoria hit the stage at the 2015 London Korean Festival on August 9th with performances of "Red Light" and Amber's solo track "Shake That Brass". The group drew a lot of cheers from their fans in London, and did a great performance despite the obvious absence of former member Sulli.
On August 7th, SM Entertainment confirmed every fan's fear and announced that Sulli will no longer be part of f(x). In a brief message, the agency said "After having negotiations with Sulli, who's still on a break, and discussing her future activities, we have decided to support her desires. She will make her exit from f(x) to concentrate on her career as an actress." Nevertheless, Sulli has remained with SM Entertainment which will be assisting her with her future projects as an actress.
In the meantime, the remaining members of f(x) will be juggling group and individual activities as per usual.
Since last year, fans were speculating that Sulli was heading for a break-up with f(x). The rumors started when Sulli suddenly went on a break from f(x) activities shortly after the group started promotions for "Red Light". Sulli only made a public appearance during the premiere of her movie "Fashion King". Last year, SM Entertainment also confirmed that Sulli and longtime rumored boyfriend Choiza of Dynamic Duo are indeed dating.
In the meantime, f(x) is preparing for a comeback that is scheduled for September.