Angelica is a central character introduced as a formidable adversary who ultimately becomes a close companion to the protagonist. Her background is that of the Dungeon Empress, the ruler of the oldest and most powerful labyrinth in that world. When first encountered, she exists in a skeletal, undead state, having been dead for a long period while still serving as the dungeon's master. Her transformation occurs when the protagonist, Haruka, uses his abilities to break the curse or control over her. Through a combination of his Subjugate skill and the application of powerful labyrinth treasures, including a silver armor, a blessed band, a necromancy jewel, and a ring of pilgrimage, Angelica is able to regain her flesh and blood, effectively being reborn as a living human.

In terms of personality, Angelica is defined by a sharp contrast between her combat capabilities and her social demeanor. As a knight and former empress, she possesses unparalleled and unique strength in battle, making her a peerless fighter. Outside of combat, however, she is notably clumsy, shy, and timid. Her long imprisonment within the labyrinth has left her unaccustomed to social interaction, making speech difficult for her. She often resorts to using simple gestures, such as nods or shakes of the head, to communicate. Despite her shyness, she is deeply loyal and grateful to Haruka for restoring her to life. This gratitude is so profound that she consciously refuses to be freed from the contract that binds her to him, choosing instead to remain as his partner.

Angelica's primary motivation is her bond with Haruka, forged from their shared experiences of loneliness. Having spent an immense amount of time isolated as the dungeon's ruler, she recognizes a kindred spirit in Haruka, who also prefers a solitary life. Her decision to stay by his side rather than return to a life of solitude underscores this connection. Her role in the story evolves from being the final boss of a dungeon to one of Haruka's most trusted allies and a key member of his party. She joins him in navigating the dungeon's floors and defending the town of Omui from monster stampedes. As his partner, she helps him train and test his growing abilities.

Her key relationships are primarily with Haruka and the other classmates summoned to the other world. Haruka gives her nicknames, such as Armor Class President, though she is also one of the few people whose real name he actually remembers. While fiercely loyal to Haruka, she also develops a supportive relationship with the other female students, including the Class Representative. Rather than vying for Haruka's romantic attention herself, she actively supports and encourages a relationship between him and the other girls. The group warmly welcomes her as she adjusts to her new life outside the dungeon.

Angelica undergoes significant development, primarily in her recovery of her humanity. This is marked by her gradual recovery of speech and the return of her emotions, hinting at a deep bond formed through mutual understanding with Haruka. In later stages of the story, her development touches on the lingering consequences of her former nature. Despite looking fully human, she is still fundamentally a monster, which has biological implications. She does not experience the same physical processes as human women, which reinforces her selfless desire for Haruka to find happiness with his human classmates.

Her notable abilities are overwhelmingly focused on combat. She is described as a girl who acts as a knight, wielding unrivaled combat prowess. Her skills are such that she is one of the few individuals capable of keeping pace with Haruka, who possesses a vast and unconventional array of powers. Her fighting ability remains formidable regardless of her social awkwardness, making her an indispensable asset in the dangerous world she and Haruka inhabit.