Squid Girl is a girl from the sea who possess squid-like tentacles. She vows to invade mankind as revenge for its pollution of the ocean. Her first task is to make the Lemon Beach House, owned by the Aizawa siblings, her base of operations. However, when she accidentally breaks a hole in their wall, she is forced to work as a waitress to pay off the damages. Thus, Squid Girl begins her life on the surface, learning new things and encountering many curious visitors to the beach house.