Due to the pollution of the oceans, Squid Girl has come from the depths to subjugate humanity. However, at the initial invasion point, she accidentally destroys the beach hut Lemon. Unable to pay for the repairs, she ends up working in Lemon in recompense. Thus it is that Squid Girl came to live with the Aizawa family, consisting of Chizuru, Eiko and Takeru.
In addition, she meets many different people such as:
Nagatsuki Sanae, who likes Squid Girl;
Saitou Nagisa, who is afraid of Squid Girl;
Arashiyama Gorou, lifeguard and comrade in the quest to protect the sea;
Cindy, who is convinced that Squid Girl is an alien; and
Kiyomi, who has become Squid Girl's close friend.
With the situation as it is, will the invasion of the land ever proceed?