I'm interested and would like to hear more about the background war relating to thosw EnStars, since I don't really know much about them. Maybe with like Mizuki or Leo/Need context
Sort of reminds me the background story of Hypmic being this sort of musical revolution against this tyrannical japanese goverment, that technically overthrew the previous Japanese Empire and setup a weaponless pro-women society. Tho admittedly they're antagonist because they're dictatorial and shut out peoples freedoms, not because they actually are bad or their goals are. But basically they engage in big rap and music battles to get more freedoms.
Hi! So the war that's been mentioned is extremely complicated, but your hypnomic comparison isn't terribly far off, mostly in that the war was centered around improving the declining reputation of Yumenosaki, the school most of the Enstars cast attends.
There's an entire wiki page dedicated to The War that I would recommend you read, but in essence its a fight between two main groups, known as Fine (usually refered to as Ex-fine to distinguish it from the current Fine) and The 5 eccentrics.
Since you mentioned/asked about Mizuki specifically, I'll talk about her and Shu (her cousin for this au)
Shu was part of the 5 eccentrics, and the existence of this group was framed as the reason Yumenosaki idols couldn't get work and saw a declining reputation (it was actually the poor work ethic of the rank and file students that caused this but its always easier to put the blame on someone else)
The Fine at the time would eventually systematically 'execute' (of a social sort, not literal) four of the five eccentrics, three of which were during live shows.
For Shu, his unit, Valkyries', audio was sabotaged and it was revealed that, due to Shus extreme pride, perfectionism, and controlling (pretty toxic) nature towards his unitmates, Valkyrie had been using prerecorded audio. This wrecked Valkyries reputation and they went on hiatus for a bit.
Afterwards, Shu would isolate himself at home and Valkyrie went from three members down to two, eventually making a return in a healthier form.
In this Au ,Shu hids out at the Akiyamas instead of his own house, and Mizuki does her best to care for him when she's home skipping school. Though her efforts aren't exactly the best, since she was both in Middle School and dealing with her own problems. Shu feels more than a bit guilty about making her do that. Mizuki does manage to get at least some idea of what happened, but Shu isn't exactly forthcoming with her about the whole War until later.
There's a lot more to say about the war, but like I said it gets very complicated very quickly, so I'd definitely recommend the Wiki page about it that I mentioned