Ikuya Ogura is an American biophysicist who appears in the anime Ajin. He is a man in his late forties to early fifties, with brown hair and brown eyes. His posture is often slouched, he is frequently seen smoking, and he typically wears casual attire such as a blazer with a graphic t-shirt, which often features philosophical sayings like "I know nothing except the fact of my own ignorance."

Born in Japan to a Japanese father and an American mother, Ogura moved to the United States in 1999 to pursue research on Ajin. His scientific thesis on the subject was considered absurd by Japanese researchers and was viewed as fringe by the American scientific community, yet he still managed to secure a position in an Ajin research department. This background establishes him as a knowledgeable but unorthodox scientist who operates on the margins of mainstream acceptance.

Ogura possesses a careless and nonchalant personality, rarely taking serious situations with the gravity others expect. This demeanor is most notably displayed when he is captured and threatened with torture, an act to which he reacts with dark humor and surprising indifference. He demonstrates this by casually requesting cigarettes during his interrogation and making light of his captor's threats. When told he would be putting his life in danger, he shrugged it off with a dry remark. This behavior is suggested to be a defense mechanism developed from enduring significant past pain, as he notably states that physical pain does not compare to emotional or mental suffering.

As a biophysicist, Ogura is exceptionally well-informed about the scientific aspects of Ajin, even if his appearance and attitude do not immediately suggest it. His primary role in the story is as a source of crucial, advanced knowledge about the nature of Ajin and their abilities, particularly regarding Invisible Black Matter and the Black Ghosts. His theories provide key explanations for the mechanics of the Ajin world, including the formation and behavior of Black Ghosts, the limits of their manifestation, and the underlying principles of Ajin immortality. He theorized that Ajin possess an unknown form of matter in their bodies which replaces lost tissues and nutrients, enabling their regeneration.

Ogura is forcibly brought into the main conflict after the antagonist Satō attacks a research institute. He is kidnapped by Yū Tosaki, who seeks to extract valuable information that can be used to stop Satō and save Tosaki's career. During this abduction, Tosaki kills Ogura's bodyguard, David Anderson. The public and government remain unaware of the kidnapping, believing Ogura to be dead. While being held by Tosaki, Ogura endures the loss of two of his fingers during torture, although he successfully negotiated to keep three, insisting he needed them to shake the ashes from his cigarette.

His key relationships are defined by this captivity. With Tosaki, the relationship is purely transactional and adversarial, as Tosaki views him only as an information source. Despite this, Ogura shows little outward malice or distress about his situation. He develops a more collaborative dynamic with Kei Nagai, the Ajin protagonist, taking on a role as an instructor who explains the workings of his own IBM and powers. Ogura’s overall stance is neutral; he does not show allegiance to the government, to the Ajin cause, or to his captors, but is instead motivated by a detached, scientific interest in Ajin as a research subject.

Throughout his time in the story, Ogura experiences little emotional development or change in his core personality. His defining characteristics remain his cynical wit, his unflappable composure in the face of violence and pain, and his function as the primary dispenser of scientific exposition regarding the series' core supernatural elements. His most notable abilities are not physical but intellectual, as his advanced understanding of Ajin biology and the behavior of IBM makes him an indispensable, if unwilling, asset to Tosaki's operation.