>>701257A-chan became Mori's manager after Cover realized just how much potential money they had to make with Mori. That is why Mori went from claiming she could convince her manager to do certain collabs early on to "My manager says no and that is final." There is no interholo collab ban though that is just a rrat Ina, Kiara and even Mori have blown out several times over it is just a matter of the EN girls being shy and not knowing how to break the ice with JP girls. This is also why the ID girl seem to collab with EN all the time with little issue.
... but that is boring...
ENMA is a bitch who blocks all collabs and treats Gura like fucking Rapunzel. The only reason ENMA allows ID collabs is because she fears the Peahen!