Kei Hanada is a supporting character in the Handa-kun anime, known primarily for being one of the most extreme and devoted admirers of the main character, Seishuu Handa. His defining characteristic is an obsessive desire to become identical to his idol, leading him to meticulously copy Handa's appearance. He alters his hairstyle and even his eyes to match Handa's distinctive dead-fish gaze. Hanada's most notable physical feature, however, is his own mouth, which he considers to be the one flaw that gives away his imitation. To hide this, he almost always wears a surgical mask over the lower half of his face. With the mask on, his resemblance to Handa is so uncanny that he can easily fool other students, even triggering a severe reaction in Handa's friend Koutarou Higashino, whose past trauma causes him to vomit at the sight of the fake Handa.

Hanada's personality is defined by his fanatical and single-minded devotion. His motivations are not malicious but stem from a place of deep admiration, pushing him to the extreme of erasing his own identity to become someone else. He is so committed to this persona that he takes school tests using Seishuu Handa's name instead of his own. This impersonation goes beyond just looks; Hanada also attempts to replicate Handa's talents, such as writing poems, believing them to be in the style of his idol. However, his efforts are flawed and ultimately unconvincing to those who know Handa personally.

In the story, Hanada serves as an antagonist of sorts within a specific comedic episode, representing the concept of a "fake Handa." His scheme is discovered when the poems he wrote under Handa's name circulate around the school, drawing the ire of Handa's protective fan club. When confronted, his determination wavers as he realizes the intense and potentially dangerous level of scrutiny that comes with being the real Seishuu Handa. He understands that the swarms of admirers and the pressure are more than he can handle, leading him to abandon his impersonation. His key relationship is, by definition, with Seishuu Handa himself, whom he obsessively worships from afar. He also interacts briefly with the members of Handa's unofficial fan club, who quickly label him a "phony" and a fraud once his deception is uncovered.

Kei Hanada does not undergo significant personal development or change his worldview over the course of the series. His role is confined to a specific comedic plot point about identity and fandom. His primary notable ability is his talent for mimicry and disguise. By combining his physical transformation with a surgical mask, he is able to create a version of himself that is visually indistinguishable from Seishuu Handa to the casual observer. This ability to perfectly imitate Handa's appearance is his defining trait and the source of the humor and conflict in his appearance in the story.