Crusch Karsten leads House Karsten, a preeminent noble family in Lugunica, and stands as a candidate in the Royal Selection for the next monarch. Sole heir to Duke Meckart Karsten, she displayed early maturity and unconventional interests, favoring swordsmanship and masculine attire over traditional feminine pursuits, often exasperating her father. Her worldview was profoundly shaped by a childhood friendship with Prince Fourier Lugunica, forged after he discovered her practicing swordsmanship in the palace gardens. This bond included Felix Argyle (Ferris), whom Crusch rescued from an abusive household. Fourier's encouragement solidified her resolve to embrace her identity, leading her to abandon dresses for formal men's clothing and dedicate herself to becoming a skilled warrior. At seventeen, Crusch assumed leadership of House Karsten following her successful defense against the Great Rabbit, an event showcasing her strategic acumen and combat prowess that convinced her father to retire. Fourier's death from a mysterious illness afflicting the royal family deepened her disillusionment with Lugunica's reliance on the Divine Dragon Volcanica. Witnessing the nobility prioritize the lapsed dragon pact over the royal family's demise fueled her political ambition to sever this dependency and restore the kingdom's self-reliance under a "Lion King" ideal. Physically, Crusch stands tall at 168 cm, possessing long dark-green hair, amber eyes, and a preference for military-inspired attire, including a blue coat bearing gold epaulettes and a cap. She occasionally wears armor in battle, accessorized with a red cape. Following events in Priestella, black, vein-like markings cover her body and she wears an eyepatch, results of a curse inflicted by the Sin Archbishop of Lust, Capella Emerada Lugunica. Her personality blends stoic determination with unexpected innocence. She commands through unwavering honesty, a strong sense of justice, and pride in her capabilities, yet displays naivety in believing Ferris's jokes and obliviousness to romantic advances, particularly Fourier's unrequited love. The loss of her memories to Lye Batenkaitos (Gluttony) replaced her confidence with shy reserve, though flickers of her resolve remained, such as upholding her alliance with Emilia's camp despite personal risk. She consistently prioritizes others' welfare over her own, refusing Natsuki Subaru's attempt to absorb her curse due to the unknown consequences and her belief in his crucial role for Lugunica's survival. Crusch possesses the Divine Protection of Wind Reading, enabling her to perceive emotions and detect deception through air currents—a critical asset in diplomacy. Her swordsmanship, honed under Wilhelm van Astrea's rigorous tutelage, pairs with wind magic to execute techniques like "One Blow, One Hundred Felled," a wide-ranged attack capable of striking multiple foes. She wields the sword Lion Rampant, emblazoned with her house's crest. Key relationships define her journey. Ferris remains her devoted retainer and steadfast emotional anchor; their bond, forged in childhood, leads her to trust him implicitly, though her amnesia strains this dynamic, rendering his protectiveness increasingly one-sided. Wilhelm serves as her sword instructor and butler, their mutual respect enduring after her memory loss. Her initial disdain for Subaru—stemming from his outburst during the Royal Selection—evolved into respect following his contributions to the White Whale subjugation. They later fought alongside each other in Priestella, saving each other repeatedly during the battle against Lust. Fourier's influence endures beyond his death; his dream of a stronger Lugunica became the cornerstone of her political ideology. Her story arcs include leading the White Whale subjugation after forming a tactical alliance with Subaru and Anastasia Hoshin, leveraging his foreknowledge of the beast's movements. Though successful, the campaign's aftermath left her vulnerable to the Witch Cult; Lye Batenkaitos consumed her memories during their retreat, fundamentally altering her identity. In Priestella, Capella's curse inflicted debilitating pain and physical corruption, requiring Ferris's constant care. Despite these trials, she remains committed to her vision of a dragon-independent Lugunica, a legacy honoring Fourier's aspirations.