Tsunetaka has long isolated himself within the family home, assuming the role of its protector for twenty years. When his father remarries, bringing a new wife and her two daughters into the household, Tsunetaka's displeasure manifests in disruptive actions aimed at driving the newcomers away. His particular focus falls on Yuki, whose recent private concerns and endearing qualities draw his intense scrutiny, prompting the stepmother to recall unsettling echoes of a previous event and regret a pivotal past decision.