I'm taking mental damage just from reading this series. You've got Sera, who is a failure of an idol and adult trying her best while bogged down by the weight of her highly successful sister's expectations and talent. You've got Kira, pushing ever forward to shine in fear of her sister abandoning her and to hold a stage worthy of her sister (delusion), and you've got no path forward from the current space except to separate from this codependent relationship, something both of them don't really want as they're both extremely lonely.
For how goofy and light hearted the artwork and comedy is, the subject is pretty fuckin' depressing