Zombies have surrounded the school. But the anime gun girls are still fighting to survive. Before classes, they shoot the undead for money. Maria sensei will then collect the cash to help upgrading guns & weapons. So don't hesitate to spray bullet hell on those annoying big bosses.
Just remember you can pick to manually control any hero you have unlocked. Because each anime girl use a different gun that offer new gameplay. Most of the anime gal need rapidly taping to fire, while the others need you to tap on the exact target to shoot. So find a gun that fits your play style to optimize your defense.
Also beware that not all zombie run towards to the anime girls. Some of them are actually shooter and will keep a distance. Aim your gun at those monsters first to avoid losing your HP.
WARNING: This zombie shooter gun is way too adorable like an anime...