Touya Kamijo is the father of protagonist Touma Kamijo. He and his wife Shiina raised their son outside Academy City. Touma's severe childhood misfortune caused ostracization and danger, including a stabbing attempt by a superstitious person. This incident and media exploitation led Touya to send Touma to Academy City after kindergarten, believing its scientific environment would offer refuge from persecution. Letters later revealed Touma's misfortune persisted within the city, though it shifted to primarily affect him personally.

Touya works as a traveling businessman for the Securities Exchange Countermeasure Group in a foreign investment company, preventing harmful stock trades and mergers, which demands expertise in economics and psychology. His frequent international travel fuels an extensive collection of souvenirs and good luck charms, driven by hope they might counteract Touma's bad luck. He meticulously arranges these within the family home using Feng Shui principles, privately doubting their effectiveness. This collection inadvertently generates significant magical potential through Idol Theory.

Unaware of magic, Touya's accumulation and arrangement of occult artifacts accidentally activated the global Angel Fall spell during that arc. This displaced the archangel Gabriel, swapped human identities worldwide, and nearly caused catastrophic destruction. Touya remained oblivious to his role throughout the chaos. He interacted with family members whose appearances were altered and demonstrated protective instincts when his son was threatened, though he was quickly incapacitated. Resolving the incident required destroying the ritual site within his home.

Touya's personality blends deep paternal concern with a flirtatious streak. He actively tries to alleviate Touma's misfortune and confronts danger for his son. However, he often admires other women, behavior that embarrasses him and provokes his wife's jealousy. Like Touma, he attracts unwanted female attention despite considering himself happily married, much to his colleagues' annoyance. His professional demeanor contrasts with occasional eccentricity during high-stakes situations.

Beyond Angel Fall, Touya appears in other storylines. He and Shiina visited Academy City during the Daihasei Festival as tourists. There, he bonded with Misaka Misuzu, leading to the families becoming neighbors. He expressed trust in Touma's judgment when the boy disappeared and waited at the hospital after his injuries. A South American business trip involved an encounter with a pursued young Gemstone esper. Alongside Tabigake Misaka, Touya aided her escape, faking their deaths with an exploding unmanned aircraft. Later, stranded in Silicon Valley during Gremlin's invasion of Tokyo, he grew frustrated by communication blackouts preventing contact with his family in Japan. During a meeting with Lindy Blueshake, he discussed the crisis's suspicious nature and leveraged a high-priority connection to illegally attempt contacting his wife.

Unintentionally, Touya's actions trigger significant events beyond Angel Fall. His meeting with Roman Catholic magician Lidvia Lorenzetti in Italy influenced her peaceful approach to capturing Academy City, setting the Daihasei Festival arc in motion. Furthermore, Angel Fall's fallout, specifically Gabriel's descent, became instrumental in Fiamma of the Right's plans for World War III. These instances make him a recurring unwitting instigator of major conflicts.