Natsuki and Nana live happily as a devoted couple despite their age difference. Their peaceful life is disrupted when Natsuki's unemployed nephew, Daiki, moves in. Daiki brings home casual sex partners and deliberately exposes his naked body, behaving in ways that defy common decency. Nana finds herself increasingly unsettled by Daiki's actions. After discovering that Natsuki is suffering from erectile dysfunction, Daiki forcefully makes a move on Nana.