High schooler Motoki finds his daily life upended by the intense and often overwhelming presence of his older sister and her vibrant partner. Their interactions frequently draw him into awkward situations, especially when the partner shows a keen interest in including him in their playful exchanges. At the same time, his close friend harbors unspoken desires, while another acquaintance adds to the teasing atmosphere. As tensions build, Motoki begins to wonder if the gentle Natsuki could offer a path toward a calmer existence.