Long years the world was shaken by war, and now many countries, including the Republic of Helvecia, lie in ruin. Nevertheless, life goes on, and the child of wartime years Kanata Sori joins the army to fulfill her dream – to play the trumpet. It is needless to say that the heroine possesses perfect pitch, a naively simple character and immense determination. Fate brings her to the mountain town of Seize, which is protected by the old Clock Fortress. Only war has ended; now the fortress garrison consists of only four lovely girls led by Captain Filisia Haidemann and Senior Sergeant Rio Kadzumi. Joining them, Kanata quickly realized that she had found a new family, which includes not only new comrades-in-arms but also almost all the local residents. But not everything is so simple in the mountain region. Very soon friendship, music, mysticism and ancient legends will give birth to a new exciting story…