As a young lowborn girl, Casca considered hardships such as starvation and abduction to be a normal fact of peasant life. Even then, she did not expect the kind of trouble that would befall her: at age twelve, Casca suddenly found herself fighting back against a pedophilic noble who told her parents he would offer her employment in his home. When the noble attempts to have his way with her after a failed escape attempt, Casca repeatedly punches him while her blouse is torn off. Griffith appears at the last second to force Casca's attacker off her while offering her his sword to personally kill the noble, which she did. From that point on, Casca joined the Band of the Hawk to become stronger despite being haunted by her past.
Golden Age ArcEdit
Years later, Casca confronts Guts under Griffith's orders when Guts defends himself against an ambush party led by Corkus. She and Guts battle until Guts knocks her off her horse. Only then does Guts realize he was fighting a woman. Griffith intervenes. He then orders Casca to cuddle the almost mortally wounded and unconscious Guts for two days to keep him warm. She later punching Guts in the stomach once he comes to. Though Casca kept those among the Hawks from killing Guts after Griffith made him join their company, she showed no respect towards the swordsman. It was later revealed that Casca felt threatened that she was being replaced by Guts as Griffith's most trusted subordinate, made worse when Griffith had romantic desires for the Midland princess Charlotte.
During a battle between the Hawks and Chuder's Blue Whale Knights, Casca silently suffers from menstruation as she knocked off her horse by Adon Coborlwitz. Though saved by Guts as he drives Adon off, she ends taking him with her into the river below. Luckily, Guts manages to get himself and Casca out of the water before dragging the latter into a nearby cave. Despite them both being freezing cold, Guts couldn't risk lighting a fire and decides to keep her warm with his body heat after stripping her of the wet clothes. When Casca comes to, punching him upon learning he undressed her prior to covering her in a blanket of leaves, Guts listens to Casca's story of the early days of the Band of Hawk along with the reason for her animosity towards him. When the two were found by the Blue Whale Knights, Guts covers for Casca so she can reach Griffith and manages to despite nearly being ravaged by a few of Adon's men. Later, during the Battle of Doldrey, Casca personally kills Adon while succeeding in taking the fortress. By that time, Casca developed feelings for Guts and becomes utterly conflicted when he leaves the Hawks. This results with Griffith's downward spiral that forces Casca to take leadership of the Hawks when they are labeled outlaws by the King of Midland after he arrested their leader.
A year later, still embittered with Guts for causing the chain of events that destroyed Griffith despite coming to help free their ally, she takes him away from the rest of the Hawks to vent her rage on him in a brief sword-fight and suicide attempt. But when Guts saves her from taking her life, Casca and the swordsman reconcile and come to acknowledge their relationship as more than comrades. The two proceed to make love that night before they and the others proceed with saving Griffith, only for Casca to attempt to convince Guts to leave her as she resolved to take care of Griffith after they learn he has been damaged and tortured. But when Griffith invoked the Eclipse, Casca watches Pippin and Judeau die protecting her before the Apostles grab her and proceed to strip her of her clothing to have their way with her. But the Apostles are stopped by Griffith after his transcending into the last of the God Hand is complete and, knowing Guts loves her, proceeds to sexually violate the half-conscious Casca in front of him. Following the Eclipse, Guts learns of the damage the event caused on Casca's mind and she gave birth to a fetal creature that was their biological child altered by Griffith's essence. As the elven cave near the blacksmith's house could protect her from the restless spirits and other fell things, Guts decided to leave Casca with Godo as he left to hunt the Apostles and find the God Hand.
Two years after Guts left her in the care of Godo, Casca walked off by chance and ended up in the company of a harlot named Luca whose group are among the refugees to St. Albion. Along the way, the refugees are ambushed by would-be assassins of Mozgus and Casca nearly got herself executed out of interacting with one of them where it not for Luca. Knowing her as "Elaine" and wanting to keep her safe from targeted by men who would take advantage of her vulnerable state, Luca wrapped bandages over Casca to make her appear to be infected with syphilis by the time they reached St. Albion.
But only a day after Casca reached the city, her presence causing the restless spirits of the starved to stir, her cover is blown as the cult dedicated to the Goddess of the Flame believes her to be a witch and conducts a ritual to marry her to their leader. However, pandemonium breaks loose when the pagans are possessed by those they killed for food in their blood orgies and the Great Goat is turned into a monster. Luckily, having had a vision of her burned at the stake, Guts arrives to save Casca. But despite Guts entrusting her safety to Isidro, Casca ends up being captured and taken to the Tower of Conviction.
After sunset, brought before Mozgus who placed her in an iron maiden in an attempt to bleed her to death upon seeing her brand and denouncing her as a witch, Casca's presence within the tower awakens the spirits of those who died of torture in its bloodstained walls to form a blood blob that consumes the living. Casca only survives himself engulfed by blood as the Demon Child exhausted most of its life force to protect her from both the spirits and the torrent of flame from a recently transformed Mozgus. Believing her death will cease the spirits' attack inside and outside the city, Mozgus attempts to have her burned at the stake with the refugees helping build the pyre. But Guts kills Mozgus and saves Casca, unwillingly allowing the the Incarnation Ceremony to run its course. By sunrise, seeing a reconstituted Griffith among the tower ruins while surrounded by Kushan soldiers, Casca is taken away from the ruins of St. Albion by Guts in the aftermath.
Falcon of the Millennium Empire ArcEdit
Casca has a difficult time reconnecting with Guts, worsen when he got possessed by the darkness with him as he was nearly made to strangle Casca to death. Though Guts stopped himself in time, he lost Casca's trust and become more difficult to protect. It was only when Farnese, Serpico, and Isidro found them that Guts decided to allow them to travel with him as added protection for Casca. Farnese remains for quite a while the only one in the group who Casca will cooperate with, and she is repeatedly put in danger when monsters attack or she escapes Farnese's watch. Farnese is for quite a while resentful of her and her inability to take care of herself, or to recognize the great love Guts has for her. She is taken prisoner by the trolls in Qliphoth, which leads to the attempt to rescue her and an encounter with one of the God Hand. On the beach before entering Vritannis, she had her first encounter with the "moon child" who she seems to recognize and is determined to protect. She remains in the background for much of the Vritannis incident's chaos, but things begin to pick up again when on Roderick's ship. By now she has begun to let Guts near her, but her childlike mind still causes trouble and she nearly leads both herself and Guts to their deaths.
Another encounter with the moon child is had on the island where the Sea God lives, during which the potential for her and Guts as mother and father is shown, even as broken as they are. Speculation is made around what exactly the moon child is, with Schierke wondering if it is King Hanafubuku. When landing at Elfhelm it was learned through one of the witches that King Hanafubuku can look into peoples' hearts and restore memory, meaning it is indeed possible to heal Casca. Upon hearing this news Guts smiled more deeply than he has in years, causing Farnese to look on jealously, the party discover the Flowerstorm king is in fact actually one of the witches who welcomed them: Danann
After sentencing Puck and Magnifico to a day of community service when the two's collaborative plot to overthrow her is brought into light, Danann asks Guts to remain while requesting Schierke, Ivalera, and Farnese to accompany her and Casca. Once in a mushroom filled chamber, Danann explains to Farnese and Schierke that the Passage of Dreams ritual requires them to astral project themselves into the mind of Casca and travel through its recesses. But Danann warns them that the world of a person's mind is a more difficult place to move about in compared to the Astral Plane, Schierke and Farnese entering into Casca's dreamscape after being put to rest. The two women initially find Casca's dreamscape to be a series of childish scribbles with a shadowed silhouette meant to represent Guts, guided by Danann's petals to their destination: A mental recreation of the Eclipse where they find the damaged doll that represents Casca's damaged mind.