Danjuro Eiga is a first-year student at Muroe High School and a key member of the school's kendo club, where he serves as the captain by the end of the series. With a round, plain face and gray hair, he initially appears unremarkable, but his character is defined by a surprising combination of natural talent, high intelligence, and a deeply devoted personality.

Eiga originally intended to join the table tennis club, but after discovering his school did not have one, he joined the kendo club alongside his friend Yuji Nakata. Despite his somewhat dim-witted or simple demeanor, he is exceptionally perceptive and academically gifted, having earned second place in the regional exams for first-year students. His quick learning ability extends to kendo, a sport in which he has no prior experience. He rapidly improves, demonstrating a natural aptitude that leads his more experienced friend Yuji to believe Eiga might surpass him before they graduate. At one point, Yuji even remarks that Eiga was made for kendo. An accomplished artist, he is also shown to be skilled at drawing.

The most defining aspect of Eiga's character is his relationship with his girlfriend, Miyako Miyazaki. Their romance is a constant surprise to others, as Miyako is notably beautiful while Eiga has an unassuming appearance. The pair are completely smitten with each other, frequently using saccharine pet names like "sugar lumps" and "honey buns" and offering each other unwavering support. Eiga is uniquely perceptive regarding Miyako's feelings and needs, understanding when to give her space or offer comfort. This is particularly significant because Miyako possesses a dark, malicious aura that she often turns on others. Eiga is the only person she would never direct this side of her personality toward, and he is uniquely capable of calming her when she becomes riled up into that dark state. In a subtle reflection of their compatibility, Eiga himself is hinted to have a similar, though less intense, dark side, which briefly manifests in his eyes during a confrontation with the kendo club's instructor. The origin of their relationship is unusual; it is said that Miyako began dating him because he resembled her pet pangolin.

Within the kendo club, Eiga's role evolves significantly. He begins as a somewhat unmotivated beginner who finds basic training boring, but his passion for the sport grows alongside his skill. Despite his late start, his leadership abilities become apparent. During a practice session with children at a dojo, he quickly earns their admiration. By the conclusion of the anime, his growth and capabilities are recognized, and he is named the new captain of the Muroe High School kendo club.