The action of the original source game takes place in 2045. Humanity confronts mysterious beings called Irosu, which appear seemingly out of nowhere, and ordinary girls take up the fight against them. These girls are called Hosimori (Star Guardians), and there is a special school for them — the Women"s Academy of Sindzhu Gammin. The player assumes the role of a teacher at this school, whose task is to train the girls so that they can repel Earth from the aliens.
