Kanon and Chiaki fend off an attack from invaders from another world.
At the same time, Haruno and Fuyuka, who had been missing, return.

As the invasion from the other world intensifies, the four heroines cooperate to confront multiple enemies.

However, in the midst of the battle, a mysterious Extear appears and engages in a fierce fight with Haruno and the others.
After barely managing to win, they find a young girl named "Shigure" who has lost her memories.

Help Shigure regain her memories through your interactions with her,
and stand up against the endless invasion from the other world!