High school girl Kana decides to take the step toward a physical relationship with her beloved boyfriend, Kazuki. For her, this moment is the most important of her life. Desperate not to fail, she realizes she must practice—and to do so, she turns to her grandfather, whom she cares for at home. Though his body is frail, unclean, and emits a foul odor, he becomes her secret partner in mastering first kisses, handjob techniques, blowjob skills, and even full intercourse—all in preparation for Kazuki. For Kana, her feelings for him outweigh her own emotions, driving her to do whatever it takes. Her pure devotion is what fuels every act.