Shinya is the manager of a small coffee house staffed by his twin stepsisters Chiyori and Chika. When a franchise for a large café chain opens across the street, the siblings are forced to improvise to hang onto their business. The girls start wearing revealing costumes to attract more clientele, although when regular customer Aya becomes close to Shinya, it inspires feelings of jealousy in Chika. Chika decides to seduce Shinya herself, although this soon causes problems for her twin, whose feelings towards him remain purely platonic. Erotic high jinks ensue.