Kai Anne Inge Fischer was born in Prague, Czechoslovakia, to a senior public servant, and her family moved to Munich after the war. She completed her matriculation and started working as a stenographer, eventually transitioning to a photo model and mannequin. Despite lacking formal dramatic training, Kai made her stage debut in cabaret at Walter Novak's Schwabinger Brettl, a renowned institution in Munich's nightlife.
By the mid-1950s, she began acting on screen, quickly typecast as seductresses, ladies of easy virtue, hard-boiled publicans, or gangster molls. She occasionally appeared in international productions, such as the tongue-in-cheek period drama The Hellfire Club or the Johann Strauss Jr. biopic The Waltz King. Kai found herself more at home playing robust characters in popular Edgar Wallace adaptations, like Room 13, The Inn on Dartmoor, or The Monster of London City.
From the mid-1960s, she began making exploitation films with an emphasis on sex, as well as assorted European potboilers, including spaghetti westerns, low-budget shockers, and erotic comedies. In the mid-1960s, Kai started transforming her image by creating the character of a female sleuth for her own series, Die Karte mit dem Luchskopf, thereby entering a genre previously dominated by men.
In 13 episodes, her character, Kai Fröhlich, solved cases by going undercover, with her agency run by an imaginary Mr. Luchs. Kai's image transformation continued through the 1970s and 1980s with more serious roles in films like Wim Wenders' The Goalie's Anxiety at the Penalty Kick and as a guest star in TV episodes of Der Kommissar, Derrick, and Tatort. She also found popularity as the circus dompteuse Tiger-Lilli in the miniseries Salto mortale and released an album of "naughty songs" under the title Kai Fidelity.
In 1984, Kai operated several photography shops in Munich and has also authored crime novels under various pseudonyms.
