YouTube Reference is Megaman 4 Dr. Cossack Stage 3 (from 0:17):
/watch?v=tplNELIi7J4&t=88s
Not sure if that is exactly what you want for your game camera to do.
Didn't tried your capx, and would'v been pointless to.
If you want that you need a continuously moving camera. (to move the camera left or right depending on the stage progress End target line... u just set scroll position X to scrollx+1 or -1 on a everytick condition)
If you don't want that, and you only want the camera to follow the player when the player is near the edge of the camera/visible screen then try this capx.
Edited: to be more clear, if you want the movement from the 0:17 seconds, at start camera doesnt move but then the player moves past the middle screen and camera starts rolling to right, to do that you create a variable that will act as a trigger, and say something along the lines
if character X >= 400 lets say is the middle of screen, set variable trigger to 1
if trigger =1 (system expression) scroll to X position ... scrollx+5
I updated the capx above is written in C3 now even though is a capx files, try open it with C3.