Don't read this, it's not important or relevant in any way for the main story, it's just full of cheap fan service.
The reason why Idolish7 is great is because of it's good story and character writing but while reading this I was feeling like I'm reading something completely different, I guess if you are a fujoshi than only you will love this otherwise there is nothing good in it there is no story, substance or any kind of development here at all, just fan service here and there, so don't waste your time by reading this and just stick with game story and anime.