YouTube Reference is Megaman 4 Dr. Cossack Stage 3 (from 0:17):
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.