Ewen Egeburg is a first-year student at Eden Academy and a member of Cecile Hall, Class 3, where he is known as one of the most loyal companions to Damian Desmond. His background is that of an heir to the Egeburg family, and his friendship with Damian and Emile Elman began in nursery school, solidifying his role as a trusted confidant early on.

In terms of appearance, Ewen is a young boy with light skin and an elongated head shape. His most distinctive feature is his blond hair, which he typically wears styled high and combed back; this creates a unique silhouette often compared to a peanut, and when unstyled, his hair reaches about chin-length. Like all male students, he wears the standard Eden Academy uniform, consisting of a black button-up shirt, black shorts, long white crew socks, and black shoes. A common sight is Ewen carrying an extra bag in his arms alongside his own schoolbag, which is understood to be Damian's.

Ewen's personality is defined by fierce loyalty and genuine care for his friends, particularly Damian. While he can initially appear arrogant and dismissive towards those he considers of lower status, such as Anya Forger, this behavior stems from a protective instinct and a deep-seated belief in Damian's potential to become a great leader who will improve Ostania. He addresses Damian with the respectful title of Lord Damian and is devoted to following him, yet this does not prevent him from showing a mischievous streak or offering candid advice. For instance, he and Emile once exploited Damian's fear of earthworms to tease him, and he has openly suggested that Damian needs to expand his vocabulary to be more effective. Beyond his role as a follower, Ewen harbors a strong personal passion for space exploration, and his primary motivation is to one day become a cosmonaut.

Within the story, Ewen serves as a supporting character who enriches the school-life setting of Eden Academy. His role is predominantly defined by his relationships. His bond with Damian Desmond is the most significant; he shows great respect for Damian and demonstrates his loyalty through actions both great and small, from holding Damian's backpack during their commute to leaping into a river to save him, despite knowing that he cannot swim. He also supports Damian academically, urging him to focus on his weaknesses, such as language arts, and joining his efforts to earn the title of Imperial Scholar. His relationship with Emile Elman is that of a close friend and partner; together, they function as Damian's primary companions and are often seen acting in unison. In contrast, his relationship with Anya Forger is initially hostile, as he tries to protect Damian from her and looks down on her for her lower class status, once worrying that she might spread peasant germs. However, this dynamic shows signs of development when Ewen discovers that Anya also shares a love for space adventures, leading to a moment where they happily chat and play together, setting aside their usual squabbles. His relationship with Becky Blackbell is similarly strained due to her close friendship with Anya. He also holds a humorous misunderstanding about Anya's father, Loid Forger, believing him to be a violent and corrupt doctor based on a creative report Anya wrote.

Ewen demonstrates notable abilities that extend beyond his academic support, where he shows a strategic understanding of study techniques and examination weaknesses. While not an exceptional athlete, his defining trait is his impulsive bravery and unwavering loyalty when his friends are in danger, such as his reflexive leap into the water to save Damian. His most distinctive personal ability is his extensive knowledge of space and rockets, which he is always eager to share with anyone who will listen.