Ex-mass murderer turned hitwoman, Koumori Kuroko loves lesbian sex and annihilating her target. Even though she is now a hired assassin by the Japanese police force, she has a record of murdering 715 people in the past since her childhood. Now she partners with Tozakura Hinako, a wildly lighthearted and innocent yet bold girl that drives like an absolute maniac, to destroy other mass murderers that are deemed unstoppable by normal means.
Murcielago provides examples of the following tropes:
- Anti-Hero: Kuroko, either of the unscrupulous or nominal variety.
- Ax-Crazy: Kuroko in spades.
- Batman Gambit: One of the early targets is a professional wrestler who is so pumped full of steroids he's now more monster than man. He's too physically powerful to take head-on, but he's also hallucinating that he's in a wrestling match where he is the Face. Kuroko tricks him into stopping a direct hit from a car, breaking both arms in the process (since it's the face's job to absorb the heel's assault,) and caps him when he's defenseless.
- Cool Car: Hinako's Murcielago, which the series is named after.
- Drives Like Crazy: Hinako
- Psycho Lesbian: One of the few instances where the two are probably not interlinked.
- R-Rated Opening: Chapter 1 opens up with Kuroko having sex with Chiyo (who has yet to be properly introduced) towards the beginning.
- Razor Wire: The antagonist of the pilot chapter uses this as his Weapon of Choice.
- Serial-Killer Killer: Kuroko would be on death row, but she's allowed to act on the police's orders to kill other psychopaths.
- Sociopathic Hero: Kuroko.
- Tragic Monster: The pro-wrestler antagonist wanted to get stronger for the sake of his fans, hoping that they will come back to watch him perform. Unfortunately, he turned to doping using a Psycho Serum.