When office worker Saki Watase finds herself low on funds, she ventures into an unusual side job—reviewing XL condoms. However, she hits a snag as she realizes none of her acquaintances require such a product. One fateful night, her strict boss Keisuke Sudou, who often scrutinizes her performance, escorts her home and discovers the stash of condoms in her apartment. Surprisingly, Keisuke, needing XL condoms himself, proposes they collaborate on enhancing the range of available options. Thus begins their discreet affair, justified as research for their reviews. As Saki and Keisuke engage in this secret liaison, they dread the eventual depletion of condoms that would mark the end of their forbidden relationship.