Erika is the adopted daughter of the skilled blacksmith Godo, living with him in his mountain cabin. She was an orphan of war, discovered by Godo amidst the ruins of a burned village, and he took her in and raised her as his own child. Her presence proved transformative for Godo, as she was said to be the only person who looked at him and saw a human being rather than just a blacksmith, helping him rediscover his own humanity.

Erika is a cheerful, lively, and curious young girl with a bright and innocent disposition. Despite her youth, she displays a surprisingly mature and responsible side, particularly when a situation demands it. She is known for being outspoken and not mincing her words, yet she holds no grudges and is quick to empathize with the struggles of others. This kindness extends to her interactions with various characters; for example, although the magician Dhaiva had previously manipulated her into doing chores, she did not hesitate to offer him a special brace for his aching leg. Furthermore, she is one of the few individuals unafraid of Guts's harsh demeanor, instead taking a liking to him and showing him genuine warmth.

Her role in the story becomes most significant after the traumatic Eclipse. Erika is the first person Guts sees upon his return, and she immediately informs him about the arrival of Rickert and the wounded Casca. In the following years, she plays a crucial part in caring for Casca, whose mind has regressed to that of an infant. She takes on this responsibility with a dedication and maturity that belies her age. After Godo passes away from old age, Erika's guardianship is assumed by Rickert, and the two form a close bond as they continue to live together in the blacksmith's home. She is present when Guts returns with Casca to the mountain hut and expresses a heartfelt wish for everyone to live together as a family, a desire that Guts struggles to accept as he is torn between his quest for revenge and his bonds with his companions.

As the world changes and becomes overrun with fantastical and dangerous creatures, Erika's peaceful life becomes untenable. She follows Rickert on a journey that ultimately leads her to the great capital city of Falconia. She remains a figure of basic human decency and courage, as seen when she insists on accompanying Rickert after he publicly defies Griffith, forcing them to flee. During their escape, she demonstrates quick thinking by retrieving a small rocket device from a wagon, which proves essential in helping the group evade their pursuer, the assassin Rakshas. Along with Rickert, the sorcerer Dhaiva, and the warrior Silat, Erika escapes Falconia and begins a new journey toward the land of the Bakiraka. Throughout the series, while she does not engage in combat, she shows an interest in blacksmithing and has a familiarity with tools and Godo's creations, having helped with small tasks and even assisted in presenting Guts with his mechanical arm.