Tomoka Kusunoki, Iku Yuki’s junior high school best friend, harbors an obsessive romantic fixation on Yori Yuki, Iku’s twin brother. She initiates a physical relationship with him to steer his focus away from his sister, but Yori abruptly ends their entanglement after admitting his feelings for Iku, leaving Tomoka embittered and consumed by jealousy. Refusing to relent, she follows Yori to high school, relentlessly attempting to revive their bond despite his steadfast rejections. Her unrequited longing twists into vengeance as she devises plans to expose the twins’ secret relationship, manipulating events to cast doubt on their interactions and threatening blackmail to force Yori back into intimacy. Her vendetta climaxes when she arranges for Iku’s assault by classmates—a ploy intended to shatter the siblings’ connection. Instead, the attack unveils their clandestine meetings, leading to Yori’s expulsion. Tomoka’s actions, fueled by rejection and a craving for control, falter in dismantling the twins’ bond. Her relentless interference underscores her refusal to accept defeat, cementing her role as an agent of conflict who strains their resilience and lays bare the ruinous fallout of envy and deceit.