Her older sister, Nene, who is planning to get married soon, is such a clean freak that she can't kiss her fiancé, Izumi. Worried that the vow kiss at her wedding won't go well, Nene asks her younger brother, Tomoki, to practice kissing with her. Will Nene be able to kiss Izumi safely? What will happen to her relationship with Tomoki? Tongues intertwined, saliva mixed together, the practice of kissing became serious before I knew it.