Gin and Vodka

The mysterious members of the Black Organization and the ones responsible for turning Shinichi into Conan. Only their codenames are known and their exact relationship to each other isn't clear, but Vodka calls Gin "Aniki" which roughly translates as brother, so it is possible that they are related (even if they look nothing alike). Vodka seems to act at the brawn while Gin seems to be the brains.

Gin

The most sinister of the pair, Gin is a cold-eyed, ruthless man with a frightening smile. He is the one who killed Haibara's sister and is intent (one could say he's almost obsessed) with finding, and killing, Sherry (he does not know that she is Ai Haibara). It's unknown what his position is in the Black Organization, but he seems to be pretty high up. Gin is intelligent and often picks up things quickly; he's also one of the few people who can see through Vermouth's disguises. He drives a large black car of a type not usually seen in Japan and claims that he never recalls the faces of those he has killed.

Chris Vinyard/Vermouth

She first appears in volume 24 as a glamourous US actress who doesn't speak or understand Japanese. However, at the end of the manga she is seen with Gin and Vodka, speaking perfect Japanese and planning to stay in Japan for a while. Vermouth is a master of disguise and also seems to have some sort of relationship with Gin. Also, there is some indication that her position in the Black Org. is quite high.

Publicly, Chris is the 'daughter' of Sharon Vinyard, who supposedly died a year before Shinichi became Conan, and was one of Ran's favourite actresses as well a friend of Shinichi's mother Yukiko. Ran and Shinichi met Sharon in New York when they visited Yukiko. Recent events in the manga have revealed that Vermouth is both Chris AND Sharon... she faked her death as Sharon to come back as her 'daughter'. Somehow Vermouth has discovered how not to age, but whether she is also a victim of the same poison that shrunk Shinichi is not yet known. Vermouth's true goals are unclear. She has some affection for Ran whom she refers to as 'Angel' and went so far as to hold back from hurting Ran who was protecting Ai. She also calls Conan a 'silver bullet' which may indicate that she has another agenda for the little detective in mind!

Shuichi Akai

This mysterious man showed up in volume 29 during a bus jack. At the end of the case he spoke into a receiver to an unknown party saying that the 'target' didn't show up. In volume 32 he reappeared and in volume 33 showed up intermittently, usually places where Ran was. At one point was shown in an alleyway outside the Mouri Detective Agency, watching the lighted windows. Ran is troubled when she sees him, as he is familiar to her, but at first she can't remember where from. However, later she remembers a time when she was with Shinichi in New York and how she met Shuichi, but then he had long hair and seemed to be a law officer, maybe even an FBI agent.

Later on, Ran's recollection is confirmed and Akai IS an FBI agent, one who knows Vermouth fairly well by his words. However, I've put him in the villains section as he claims that he is searching for his ex-girlfriend to make her cry "tears of blood" and his real motives are not yet clear.

Kaitou Kid/Kaito Kuroba

He's not really a villain and certainly not part of the Black Organization, but he IS on the wrong side of the law and is the one criminal Shinichi/Conan hasn't caught. A 17 year old master thief, he is a master of disguise and can change his voice, plus he has lots of nifty gadgets to aid him in his escapades. When he's going to steal something, Kid leaves the police puzzling riddles, usually only Conan can solve them. Interestingly, he can't ice-skate and he hates fish!

Like Shinichi and Heiji, Kaito also has a female childhood friend, Aoko Nakamori (the daughter of the police detective determined to catch him), but she doesn't know about his secret identity.