Jinzaburō Matoba is a high-ranking official of the Japanese government, serving as the director of the Far Eastern Cultural Exchange Promotion Bureau, a position that places him in direct oversight of the cultural exchange project with the Holy Eldant Empire. He is a middle-aged man of average build, with neatly parted black hair that shows hints of grey, and he is almost always seen dressed in a subdued, leaf-brown suit. His most defining physical characteristic is his narrow eyes, which are perpetually narrowed into a calm, smiling expression that makes his true thoughts difficult to discern.

Matoba’s personality is a complex blend of outward affability and chilling pragmatism. He presents himself with a slow, measured, and relaxed demeanor, often speaking in a calm tone that can initially come across as supportive or even mentor-like. This mask of benevolence, however, conceals a ruthless and calculating nature. He is a consummate bureaucrat, utterly dedicated to carrying out the objectives of his superiors, no matter how ethically questionable those objectives may be. In this role, he embodies a classic ruthless middle manager, trapped between the demands of high-level politicians and the realities on the ground in Eldant. Despite this cold efficiency, there are subtle hints of a more conflicted individual, as he once admitted that he did not want to carry out some of his more sinister tasks. His favorite anime is said to be Crayon Shin-chan, a detail that adds an incongruous and slightly humanizing layer to his character.

Matoba is the architect of the Japanese government's strategy for Eldant, and his central motivation is the successful execution of a silent cultural invasion. His goal is to use the spread of otaku culture as a tool for soft power, aiming to create economic and cultural dependency. By inundating Eldant with Japanese media and goods, the government intends to gain a strategic and economic foothold, eventually securing greater authority for the Japanese Self-Defense Forces and leveraging influence over the Eldant Empire's government. Matoba was the one who devised the deceptive recruitment test that Shinichi Kano passed, specifically seeking an individual who was highly knowledgeable about otaku culture but who would not be missed if he disappeared from the modern world. He then drugged Shinichi and transported him to the other world, setting the entire plot of the series in motion.

His role in the story is that of the primary antagonist and the direct superior to both Shinichi and the JSDF officer Minori Koganuma. He serves as the liaison between the main characters in Eldant and the shadowy powers of the Japanese government. Throughout the first part of the series, he maintains a facade of a helpful, if somewhat bureaucratic, boss, approving Shinichi's requests while subtly steering the project toward its true invasive purpose. The revelation of his true nature marks a major turning point, as he coldly explains to Shinichi that the cultural exchange is a calculated invasion and that Shinichi himself was chosen to be a disposable pawn. Despite this antagonism, he is a key figure in the story's resolution. When Shinichi devises an alternative plan to foster genuine cultural exchange without dependency, Matoba recognizes its efficacy and pragmatically switches sides, using his inside knowledge and a secretly recorded confession to blackmail his own government into backing down.

Key relationships define much of his character arc. His relationship with Shinichi is the most significant, evolving from one of manipulator and pawn to a more complex, cautious alliance. While Matoba initially sees Shinichi as a tool, Shinichi’s unexpected success and moral conviction ultimately force Matoba to respect his approach, even if trust is permanently broken. He is also Minori Koganuma’s superior within the Japanese hierarchy, a relationship that becomes strained when she sides with Shinichi against the government's plan. His interactions with the leaders of Eldant, particularly the young Empress Petralka, are formal and political, though she and her court ultimately come to distrust him after his true intentions are exposed.

Matoba undergoes a notable but subtle development throughout the series. He begins as the ever-smiling, unflappable mastermind, completely confident in his plan for a bloodless conquest. However, when Shinichi successfully derails the plan by proposing self-sufficiency for Eldant, Matoba’s constant smile finally vanishes, replaced by visible panic and frustration. This represents a crisis of his professional identity. Ultimately, he adapts. Rather than stubbornly clinging to a failed strategy, he aligns himself with Shinichi’s more sustainable approach, suggesting that his primary motivation is not malice but a pragmatic desire for the most effective outcome, even if it means betraying his original superiors. A piece of advice he offers Shinichi, that he will "continue to walk the tightrope as to whether something is aggression or not," encapsulates his own ongoing, morally ambiguous position.

While Matoba does not possess any magical or combat abilities, his notable skills lie entirely in the realm of intelligence, manipulation, and bureaucracy. He is a master strategist and administrator, excelling at high-level negotiation, managing complex logistical operations, and writing official documentation. His most dangerous ability is his strategic foresight and his talent for exploiting situations, from turning an apocalyptic fantasy world into a market for Japanese goods to turning a young otaku into an unwitting agent of national policy. He is a man who works from the shadows, whose power comes not from a weapon, but from his complete understanding of the systems of government and control.