An Ocean's Sword

In the darkness of the sea, the abyss slumbers, biding its time until the proper hour. Its enemies defeated, its existence forgotten, humanity would be unprepared for the coming storm. Yet in the fires of the Fourth Holy Grail War hope awakens, and stumbling onto a young Shirou Emiya, she makes her choice. And everything changes. "Admiral, aircraft carrier Kaga, awaiting orders."