Futaba Shinonome, Miharu’s younger sister, wields a bold, opportunistic demeanor paired with nymphomaniac tendencies evident since youth—contrasting Miharu’s slower development of comparable traits. Obsessed with Ushio, Miharu’s senior, Futaba capitalizes on her sister’s memory loss to infiltrate his life, drugging Miharu to sleep so she can advance on Ushio undisturbed. Her calculated seduction unfolds mere feet from her unconscious sibling, confident yet oblivious to Miharu’s unyielding grip on Ushio despite fragmented memories.

Their rivalry thrives on Futaba’s hunger to dominate romantic conquests, convinced Miharu’s amnesia guarantees victory. This presumption falters as Miharu resists relentlessly. Futaba’s manipulative tactics underscore a blunt, self-serving approach to relationships, sacrificing familial bonds for fleeting desire. Her narrative paints a portrait of ambition clashing with loyalty, where strategy meets unforeseen defiance.