For those who don't understand why Aqua is doing this remember the previous chapters.
Idol industry only shines on the outside. Backstage is way less pleasant, to put it lightly, even before adding crazed fans (which they exist irl, just look out the fame Love Live fans got and those idols don't exist). That's one of the things that got Ai killed, he just doesn't want the same thing happening to his sister.