Keith is a significant character in the anime The Villainess Is Adored by the Prince of the Neighbor Kingdom, where he holds the title of the Forest Fairy King. He is a fairy with a notable interest in the protagonist, Tiararose Lapis Clementille, and is known for his egocentric and mischievous personality. In the story, Keith takes a bold and unexpected interest in Tiararose, claiming that her soul is unusual. This fascination leads him to abduct her and bring her to his forest domain, an act that creates significant tension and becomes a major plot point that tests the resolve of her fiancé, Prince Aquasteed Marineforest. However, his actions are not purely antagonistic; he puts Tiararose to sleep under the pretext of allowing her to de-stress, and his abduction ultimately leads to her confessing her feelings of jealousy, which benefits her relationship with Aquasteed.

Keith's personality is a blend of charm and provocation. He is described as a gadfly who enjoys pushing Aquasteed's buttons, often flirting with Tiararose specifically to provoke a jealous reaction from the prince. Despite this teasing nature, he also displays a perceptive and strategic side. He is the first to recognize that Aquasteed is unknowingly causing Tiararose emotional pain by spending time with another woman, Icilla, for political reasons related to fairies, and he criticizes the prince for failing to communicate honestly with his fiancée. This behavior has led some to interpret Keith not as a true villain, but as a trickster mentor who plays the role of an obstacle so that Aquasteed can demonstrate his devotion and so that Tiararose can become more honest about her fears. His role in the narrative, therefore, is to catalyze character development and test the strength of the main couple's bond. As the Forest Fairy King, Keith wields authority over his domain and possesses the magical abilities inherent to his station, which he uses to create a "sleeping forest" and challenge those who enter his territory.