Tsumiko Horie navigates life at Reverse Cross High School in post-apocalyptic Tokyo, emerging as a compassionate and courageous student whose admiration for Kakugo Hagakure deepens into romantic longing after observing his selfless defense of civilians against monstrous forces. Her physicality contrasts with conventional manga heroines—marked by an average build and lingering insecurities about her perceived lack of allure, a trait consistent across adaptations. Her trajectory fractures when Chidokuro, an agent of Harara Hagakure, abducts her. Subjected to parasitic modification, she mutates into a grotesque moth-grub hybrid with adhesive tentacles that shred flesh on contact. A symbiotic parasite fused to her spine unlocks a secondary wasp-like mutation featuring a venomous stinger, though this form proves detachable rather than irreversible. Critical to her arc is a mind-controlled duel against Kakugo, where she chants “sticky” in a trance-like state and unleashes destructive energy beams from her forehead. The confrontation resolves when Kakugo’s kiss disrupts the parasite’s hold, reverting her to human form—a pivotal moment framing emotional connection as an antidote to bodily corruption. While the manga emphasizes her weight as a recurring “Informed Flaw,” the OVA downplays this detail without erasing her self-doubt. Her bond with Kakugo remains non-romantic yet profoundly impactful, anchored in his protective instincts. Post-recovery, she reintegrates into civilian life, her story concluding without subsequent transformations in documented continuities.