In Romantic Killer, the world’s birth rate has dropped so low that magical beings step in to fix it. Anzu Hoshino is chosen as a test subject because she actively rejects romance, preferring games, chocolate, and her cat. The wizard Riri is assigned to her and removes those comforts, forcing her into classic rom-com situations with attractive boys. The goal isn’t just chaos—it’s to push Anzu to fall in love and help restore interest in relationships.