Naoya Mukai is having the time of his life after his childhood friend Saki Saki finally accepts one of his countless confessions. Ensuring that their relationship will stay strong, he spares no effort in showering affection to his now beloved girlfriend. However, one afternoon, another girl named Nagisa Minase suddenly confesses to Naoya following months of preparation. Even though he politely rejects her, Nagisa's irresistible charm and determination continue to attract Naoya. Wanting to fulfill both Saki and Nagisa's desires, Naoya ends up proposing a crazy idea—to date the two of them simultaneously, with both girls fully aware. This unprecedented state of affairs ultimately causes wacky and hilarious situations in whatever they do to keep their unusual relationship going.

With the seas under constant threat from the hostile Abyssal Fleet, a specialized naval base is established to counter them. Rather than standard naval weaponry, however, the base is armed with Kanmusu—girls who harbor the spirits of Japanese warships—possessing the ability to don weaponized gear that allows them to harness the powerful souls within themselves. Fubuki, a young Destroyer-type Kanmusu, joins the base as a new recruit; unfortunately for her, despite her inexperience and timid nature, she is assigned to the famous Third Torpedo Squadron and quickly thrust into the heat of battle. When she is rescued from near annihilation, the rookie warship resolves to become as strong as the one who saved her.

Kouta has girl troubles of the supernatural sort. For some reason, he keeps attracting the attention (and affections) of animal spirits! Having spent most of his life in the country, Kouta is understandably nervous when he moves in with his grandma to attend a high school in the big city. He hoped to make a good impression, but having Chizuru, a beautiful fox spirit, hanging off his arm didn't seem to be the sort of image he wanted to have. She's not alone in her love for Kouta, either. Nozomu, a wolf spirit, as well as other youkai have their sights set on the hapless country boy.

Even after spending a considerable amount of time with Takagi, Nishikata is still struggling to find a perfect plan to defeat the expert teaser. A battle of wits, a contest of physical prowess, a test of courage—any strategy he employs to expose her weaknesses is to no avail. On the contrary, Nishikata's pitiful attempts only reveal more of his own flaws, which Takagi takes advantage of to become increasingly daring in her teasing attempts. To make things worse for Nishikata, rumors about him and Takagi may have spread in class due to the frequent interactions between them. However, the optimistic Nishikata believes that wisdom comes with age and that as the days go by, his experience with her constant teasing will eventually bear fruit, leading him to the awaited moment of victory. Thus, Nishikata continues to strive for the seemingly impossible—to outsmart Takagi and make her blush with embarrassment.