it isn;t called anything.
to remove it right click in the game area. and do any of the following in the flash popup that occurs.

clear cache

settings then the storage panel there drag used to 0 (if you have an old version of flash). there can be a representation of this in the following perhaps called global storage settings panel instead of the one i will describe next. but i don't know if this one works the way it used to.

global settings then webstite storage settings panel then find the relevant one for this game idolmaster.... and delete it. this might appear different depending on what kind of browser you are using, chrome based or not
reload the game. it will take a longer time to load perhaps the first several times you do this from now on. and you will get that question you answered again so answer it differently..