Keith Claes, adopted younger brother of Katarina Claes, originated as Keith Coleman—illegitimate son of Viscount Coleman and a commoner prostitute. His biological mother regretted his birth, and he endured severe neglect and abuse from his birth family, including daily harassment from his half-brothers. This mistreatment provoked his first uncontrolled earth magic outburst, injuring his tormentors. At age eight, his exceptional magical potential secured adoption into the Claes family. His arrival strained familial bonds when Millidiana, his adoptive mother, mistakenly believed him to be her husband Luigi's illegitimate child, causing further neglect until Katarina intervened to clarify his lineage.

Physically, Keith possesses a handsome appearance with ochre or flaxen hair and grey or blue eyes. By age fifteen, he stands approximately 180 cm tall. His striking resemblance to Luigi Claes initially fueled rumors about his parentage. He customarily wears formal attire: a suit with a light purple waistcoat, dark purple tie, and long white-and-purple jacket.

In the original *Fortune Lover* game timeline, Keith developed a cold relationship with Katarina and Millidiana, fostering intense loneliness. This isolation molded him into a playboy who sought validation through flirtation. His game route involved falling for Maria Campbell, culminating in Katarina's exile (good ending) or Keith murdering Katarina after failing to protect Maria (bad ending).

In the revised timeline, Katarina’s friendship transformed his development. Instead of embracing playboy tendencies, he matured into a responsible, disciplined gentleman with strong moral values, though retaining his natural charm and unintentional appeal to women. His personality radiates genuine kindness and protectiveness—especially toward Katarina—prompting him to act as her primary minder due to her oblivious nature. He battles deep-seated insecurities from his traumatic past, including fears of losing magic control and being perceived as a monster. Despite his gentlemanly demeanor, he harbors intense jealousy and rivalry, particularly toward Prince Geordo, over Katarina's affections.

Keith wields exceptionally powerful earth magic, specializing in creating and controlling large golems. His abilities rank among the strongest in his peer group, though he initially struggled with power incontinence due to inadequate training. His high magical aptitude motivated his adoption, as the Claes family required an heir after Katarina's engagement to Prince Geordo.

His relationship with Katarina evolved from mutual distrust to deep affection. While she views him platonically as a brother, Keith developed romantic feelings. He confessed after she rescued him from a kidnapping orchestrated by his birth brother, Thomas Coleman, and dark magic users—an event involving an unconscious kiss during the rescue. Post-confession, Keith actively vies for her attention, though Katarina often forgets or misinterprets his advances. Millidiana and Luigi support his romantic pursuit, hoping to annul Katarina’s engagement to Geordo. Keith maintains respect for Luigi and allies with household staff like Anne Sherry to monitor Katarina. His interactions with his birth family, especially Thomas, remain fraught due to their abusive history.

Key developments include his role in the *Pirates of the Disturbance* storyline, where he boarded the luxury liner Vinculum with Katarina during spring break. The ship’s pirate takeover forced them into a scenario mirroring a *Fortune Lover* fanbook’s doom ending. Keith also experienced a gender-bent reality via a wish-granting dollhouse to grasp Katarina’s perspective. His character arc consistently emphasizes loyalty and protection of Katarina, epitomized by his declaration: "I will never let Catarina go—not even to Geordo."