A nostalgic letter written by Krystal to her colleague and friend Sulli, a former member of the group f(x), is stirring up strong emotions on the internet.

On November 16, netizens and fans were touched by a clip from their group reality series, "Amazing (f)x." The clip shows Krystal addressing very touching words to Sulli, declaring her undying love until they both become grandmothers, and expressing her wish to always share good times and good meals. The relationship they shared back then, full of shy laughter and complicity, is described as the essence of a unique friendship at this time of life.

The letter, written when Krystal was just 20 and now 30, resonated deeply with fans, who left comments such as "Time flies," "They started so young. Sulli left us 5 years ago," and "This letter is so sad, I wish I could go back to those times."

Sulli tragically passed away in October 2019 at the age of 25, an event that continues to haunt her fans and loved ones. The recent passing of actor Song Jae Rim also seems to have rekindled the melancholy of Sulli's fans.

Relive this moving moment through the video excerpt of Krystal's letter.