Cells and Balloons belong to a particular Frame(1), but you can display in area of the other Frame.
Left Page has 1 empty Frame.
One way is “Popup(Buchinuki)”, In most cases the Cells with an alpha channel (Character etc) or Balloons to appear “over” the other Frames will work up to crossing the line.(2)
Another method is “Content Sharing” to display all the contents of the Frame including the background “by” the other Frames.(3)
To be confined to 1 page Popup scope, Content Sharing is effective facing the opposite Page. (Please see 2 and 3 in comparison)
If you set Tachikiri for all Frames in the Content Sharing Group, you can look like painting led across 2 pages.(4)