Keiko Tanaka is a significant supporting character in the comedic anime and manga series Cheeky Angel. She is a classmate of the protagonist, Megumi Amatsuka, and serves as a rival figure, often taking on the role of an antagonist driven by jealousy. Keiko comes from a wealthy and prestigious family, a background she shares with Megumi, and she possesses a conventionally pretty face along with proficiency in martial arts. Her self-esteem is very high, largely due to her status as the daughter of a conglomerate, which has led to an exaggerated sense of entitlement often described as princess syndrome.

Her primary motivation throughout the story is her intense jealousy of Megumi. Keiko believes she deserves to be the center of attention and uses her family's wealth to scheme and create competitions aimed at upstaging or subtly bullying her rival. However, her plans consistently backfire due to Megumi's unrivaled combination of beauty and physical strength, making Keiko an unlucky antagonist whose failures are a primary source of the series' humor. Despite her scheming nature, her actions are generally confined to the comedic sphere and rarely contribute to the more serious plotlines.

In terms of her role in the story, Keiko is a comedic foil to Megumi. Her elaborate but doomed attempts to prove her superiority drive many episodic gags. Among the main group of characters known as Megudan, she holds Hitomoji Kobayashi in high regard. Conversely, she frequently associates with Ichiro Fujiki and inadvertently plays a role in guaranteeing some degree of his growth over the course of the narrative. She is almost always seen with a subordinate named Shirasagi Yoshimi, and her interactions with other characters, such as Miki, tend to be surprisingly free of conflict. Keiko does not undergo a dramatic personal transformation, as her character is largely static, existing to provide consistent comic relief as her schemes perpetually fail in spectacular fashion. Her notable abilities include her martial arts skills and her significant financial resources, which she deploys in her various failed attempts to upstage Megumi.