Ataru is left alone at home while his parents go on a two-night, three-day couples trip they won in a raffle. His mother arranged for a friend to come by and help with housework and meals, but the woman who arrives is nothing like the plain acquaintance he expected—instead, it's Yuna, a stunningly sexy and seductive woman. Ataru falls for her beauty at first sight and schemes to keep her at the house. Soon, the two are spending a long, erotic night together alone.