Yoichiro Tekuno, known as Techno, grew up isolated within a bomb shelter under his grandfather's care. This confinement limited his exposure to society and typical social experiences. Both possess considerable intellect, especially in scientific and technological fields.

His worldview changes when he notices a girl, Hitomi Matsuzawa, in his yard. He develops an intense, immediate fixation on her but insists on calling her "Daisy" despite her repeated corrections. This obsession drives him to leave his shelter and enroll at her school to pursue a relationship.

His courtship reflects a scientific, technology-oriented mindset, devoid of conventional social awareness. He rehearses conversations using a robot for three months before approaching Hitomi. His methods involve intricate technological schemes meant to impress or assert ownership over her, often leading to hazardous outcomes that endanger her safety. These include enlarging her to a giant size, deploying a laser-equipped replacement teacher, generating a giant slug, and arranging her kidnapping.

His behavior displays possessive and obsessive qualities, including stalking, constant monitoring, physical confinement, and denial of her real identity. These actions lack malicious intent but arise from a severe deficit in social skills and an inability to grasp normal romantic or interpersonal behavior. He approaches human connections as scientific challenges solvable through technology.

Throughout the narrative, his personality and behavior remain largely unchanged. His actions stay focused on possessing Hitomi, and the story ends with her yielding to his relentless pursuit despite a continued absence of mutual understanding or regard for her autonomy.