Erika, a winged humanoid from the destroyed planet Baam, is the daughter of Emperor Leon and younger sister of Richter. Her royal duties included accompanying her family during diplomatic talks with Earth. At these negotiations, she witnessed her father's assassination and, attempting to restrain Richter, inadvertently caused the death of Earth delegate Isamu Ryuzaki. This act instilled profound guilt and a sense of responsibility for the ensuing war.

After negotiations failed, she served as a Baam field medic. A spaceship accident caused her amnesia and crash-landing into Earth's ocean. Found unconscious by Kazuya Ryuzaki after a battle, she formed a deep emotional bond with him during recovery, unaware of her alien heritage or his identity as Daimos' pilot. Encountering Richter during a broadcast restored her memories, revealing her role in Isamu Ryuzaki's death and creating intense conflict between her love for Kazuya and loyalty to her people.

Innately pacifistic and resilient, Erika rejected Baam beliefs of human inferiority, advocating for peace despite societal pressure. Though generally non-violent, she demonstrated willingness to use force when necessary, such as killing Gildo to protect Kazuya and Kyoshiro. She exhibited leadership guiding Baam refugees in New Zealand after Barandock's departure and coordinating resistance against the usurper Olban. Guilt over her father's death and her role in Kazuya's father's demise initially made her push Kazuya away, believing their love forbidden, though she later accepted his unwavering devotion.

Her relationship with Richter deteriorated due to conflicting philosophies, briefly reconciling before his death. Her primary confidante was caretaker Margarete, who supported her romance with Kazuya and aided her escape from Baam custody. Committed to peace, Erika infiltrated Olban's regime by agreeing to marry him, intending to assassinate him. Olban substituted her tranquilizer gun with a real weapon, causing her to unknowingly shoot Kazuya during a rescue attempt. Horrified, she later used the same weapon to kill Olban's agent Gildo.

Her arc culminated at the wedding ceremony, confronting Olban, denouncing his tyranny publicly, and revealing her assassination plot. Following Olban's defeat and Richter's sacrificial death preventing Baam's asteroid city from crashing into Jupiter, she survived to continue advocating for peace between Baam and Earth alongside Kazuya.