After losing his mother, Keita Suminoe gains two stepsisters, Ako and Riko. Their innocent sibling relationship takes a twist as both sisters develop romantic feelings for him, sparking a fierce competition for his affection. As Keita nears the end of middle school, he strives to attend the same high school as his sisters, all while navigating his complex emotions towards them. Amidst the turmoil of incestuous advances, Keita must confront his inner turmoil and decide how to handle the amorous attention from not only his sisters but also other women vying for his heart.