Female Detective Riko: The Virgin's Deep Abyss (1998)

The film centers on Riko Murakami, a tough-as-nails detective who is also the single mother of a young boy. At work, she has hit a wall investigating a grisly murder in a hotel room. In her private life, she sweats her son's impeding "park debut" -- when she introduces her son and herself to the young mothers of her neighborhood. Most give her strange almost hostile looks except Sachiko (Keiko Unno), who says her kid is in the hospital. While her son gambles about the playground, Riko and Sachiko exchange child-rearing war stories and soon become friends. Then she learns that the prime suspect of her case is none other than Sachiko's husband. Moreover, she learns that Sachiko's son was in fact the center of a kidnapping case several years ago and the child has been long thought of as dead. Her husband and the detective in charge of child's case both have their own secrets, and soon Riko finds herself and her son threatened.