Three sisters, Isuzu, Aoba, and Haruna, inherit an electronics store in Akihabara from their dead father, but their business is not doing well. Creditors have threatened to seize their shop if they cannot pay their bills. They find a heart-broken otaku named Takezou Muto on the doorstep of their shop, and he is able to save the day and the shop with his quick thinking. He is hired on permanently, and Haruna, the motherly sister, asks him to transform their store into a money-making enterprise. Takezou dreams of it becoming an otaku paradise, much to the delight of Isuzu and much to the consternation of Aoba.

The story follows the adventures of a Japanese battleship, the crew of which consists solely of girls for some reason (Current submarines are actually all male crews because of privacy concerns...). This is pure fanservice and the historical details could perhaps be questioned, but as long as you like ships, tough girls and comedy, you're still gonna enjoy it.