Kotetsu no Daibouken

The titular heroine (real name Lynn Suzuki, nicknamed Kotetsu, which means Little Iron) is a young apprentice of martial arts who flees her cruel master and is accepted by the kind lady Miho Kuon, who runs a detective agency in Tokyo. The game can be perceived as a sequel to the anime, since it begins roughly where the original story ended, with the former "nerdy" spy Tatsuya Mikado already turned good and living by Miho Kuon along with Kotetsu and other heroes. Like the original anime, the game mixes modern setting with bizarre and supernatural elements. Unlike the anime, this game contains many explicit sexual scenes.

[From Moby Games]