I don't know much about MVC2 mugenization yet I know of some basics of "off screen camera follow" MUGEN way:
1) make a way to detect the particular hit (i.e. give a particular ID# to your HitDef and the hit x-velocity should be big enough) on your MUGEN Enemy which results in "off screen camera follow"
2) then upon that particular hit confirm (i.e. MoveHit = 1 and NumTarget(ID#)), within that particular hit Statedef, use a ScreenBound with default values to lock the screen,
3) then also within that particular hit Statedef, use ChangeState to make your MUGEN character enter its "off screen" Statedef#, based on the same hit confirm condition like BackEdgeBodyDist < -20.0 or some negative values based on your MUGEN character's Const(size.ground.back) and/or Const(size.air.back)
4) in your MUGEN character's "off screen" Statedef#, use a ScreenBound with value = 0 and movecamera = 0,1 to lock the screen again, and use a PosSet with x = -240.0 * Facing and y = 0.0, may be add a NotHitBy with value = SCA too to make sure nobody can hit you when you are sending your MUGEN Enemy off screen
5) use ChangeState to make your MUGEN character enter its "dash back in/return to screen" Statedef#, which is usually a modified version of your MUGEN character's "off screen" Statedef 100 (i.e. make a Statedef 101 with the same Statedef 100 MUGEN code), based on some conditions like when your MUGEN Enemy is not your MUGEN Target anymore, or when your MUGEN Enemy is in its own particular get-hit Statedef# (i.e. HIT_LIEDOWN state), or after a certain state time (i.e. Time > ##)
6) you may want to adjust something like special "dash back in/return to screen" effects (i.e. Explod and/or PlaySnd) in your MUGEN character's "dash back in/return to screen" Statedef#
* about the x = -240.0 * Facing........-240.0 depends on how far you want to put your MUGEN character behind visible screen back edge
* remember to add a "ignorehitpause = 1" to each involved MUGEN state controller to avoid any hit pause delay you may have put in your "off screen" hit to our MUGEN Enemy
** this is not tested but it is the basics I think, so you may want to try it out yourself first to see....or the better way is to study the actual MUGEN code of the MUGEN characters (i.e. Mega Man Volnutt and Juggernaut) which offer such MVC2 "off screen camera follow" feature in MUGEN