Sadly, Symphogear is Japan-only app for now.
You want it with the not-so-legal way, use Qooapp application to bypass the proxy or something (cmiiw) to download the app.
Kinda risky actually, especially for the account safety because some games like Granblue Fantasy is hunting accounts who used illegal softwares in their games(dunno about the details but the admins said that it's permaban for whoever uses illegal means)