What is the story of Flower Sea among tfboys fans, and why is it always mentioned?

The blue ocean represented by Karry, the red ocean represented by Jackson Yi and the green ocean represented by Roy divide the scene into three pieces, among which several orange lights are scattered everywhere alone.

Judging from the programs prepared by the three children at the scene, they want to convey to the fans the idea that they are still a group. Most of the songs were written by three people. The interaction in small details and eye contact between performances made people obviously feel that they were the three children before, and they were the group we watched grow up with. But fans are not grateful.