The story follows a small-time detective, his brother (who runs the business side of things), and two high-school summer interns (nick-name ManAya for the both of them). They get involved in a case where teenage girls burst into flame, turn to glass, then disintegrate. It is their duty to locate and protect one of these Glass Maidens, code name HW-9, from Kito and his organization.
Glass Maiden provides examples of the following tropes:
- Amazon Brigade: Tito's squad consists of grim-faced gunners.
- Camp Gay: Porilyn, large crossdresser who considers himself feminine.
- Cool Car: Shu's Pontiac Firebird (Trans-Am).
- Cosplay Otaku Girl: Monica dresses up for Doc after hours.
- Deadpan Snarker: Ayaka is noted in-universe for speaking in a monotone.
- Genki Girl: Manami, with an unkempt head of orange hair and a motormouth.
- Gratuitous English (writing in OP and lyrics in the ED)OP: Never looking back ...I'll get startedED: Que sera-sera. All right! Don't take it too hard ... in this time ... Lonely hearts ...music ... Have a ball!
- In-Series Nickname: AyaMana = Ayaka + Manami
- Jazz: Both the OP and ED.
- Lovable Sex Maniac: Doc (Sensei) loves to spend after-hours filming Monica displaying sexy outfits.
- Mascot: Lil Q (Q-chan), the dog.
- Red Oni, Blue Oni: Manami, red to Ayaka's Blue.
- Surveillance Station Slacker: Porilyn's security room shows view from around (and outside) the city.
- Taken for Granite: Sara and the other Glass Maidens.
- Shu: Head of detective agency, the main protagonist, and an incorrigible lady's man.
- Akira: Shu's younger brother, is referred to as 'Mini-Boss'. His job is to bring in work for the company.
- Ayaka: Speaks in a monotone and is usually seen at her computer.
- Manami: Overenthusiastic assistant, wants to get credit as a detective, and is dominant in the ManAya pair.
- Sara: AKA HW-9, is the titular Glass Maiden. She can revert from glass to human and runs a consistantly high internal temperature.
- Porilyn: An effeminate man that is the source of many of the agency's assignments.
- Sophie: A disrespected reporter who knows more than what the police will admit.
- Doc: A competent but pervy doctor. His clinic is just below the detective agency.
- Monica: The sexy nurse, loves to cosplay for Doc.
- Kito: The chief antagonist and leader of an all woman brigade.
- BW-Alpha: A quiet girl who hides her true form which is ultimately fierce and dangerous.