Gin and Sherry
Gin and Shiho Miyano were both members of the Black Organization until Shiho escaped after he killed her sister Akemi Miyano. Gin seems especially interested in hunting for the escaped Shiho while she is unusually terrified of him.
 Current Timeline
It is strange that Gin and Shiho seem to know a lot about one another despite being in entirely different divisions of the Organization. They clearly have a connection outside of their professions to account for knowing each other so well.
On his part, Gin clearly knows Shiho's personality very well as he can anticipate her movements despite having rather different lines of work. Gin can identify her from a single hair with conviction.
As for Shiho, she hardly knew most of the other agents in non-science related positions. She hadn't met Pisco since she was a baby, she had only heard of Korn and Chianti, and hadn't heard of Kir. Conan never asked about Tequila. Shiho knows Vermouth despite not being in science because Vermouth likely had a connection with Atsushi and Elena Miyano and their research because Vermouth doesn't seem to age. Gin is on the assassination side of things, so it is anomalous how well she seems to know him given how she doesn't know much about anyone else outside of the research branch.
 Romantic Relationship
The events of the Reunion with the Black Organization case open the possibility that the reason they know each other so well is because Gin and Shiho had a romantic mutual relationship. In Haibara's dream, Gin describes their meeting as a reunion: "This is the end of your wanton sporting... Now, wake up from your dream... Shouldn't we celebrate our reunion with your favorite color scarlet... right, Sherry?" Haibara uncharacteristically yells "Don't touch me!" when Ayumi places her hand on Haibara's arm, snapping her out remembering her dream. Later, the real life Gin thinks of her naked once, looking forward to their meeting with one another. Cases later, in the Mystery Train case, he does so again.
Furthermore, when the two of them meet on the rooftop of the Haido City Hotel, there are more suggestive exchanges. Gin purposefully chose not to do his job in the most efficient fashion -shooting Shiho in the chimney- but instead chose to make a special exception for her by waiting out for her on the snowy rooftop because killing her there would be, paraphrasing, more beautiful. She even gets into the act by thanking him, albeit sarcastically, for "waiting for her in the cold"; Shiho seems to purposefully be alluding to the stereotypic scenario of one lover waiting for another in poor climate. Gin also makes a comment about her disguise, the uniform and the glasses, being unsuitable for her, which carries an implication that he thinks there is some other outfit which would be more suitable.
He also seemed express some sort of jealousy over that Shiho has been getting help from a 'man'. It sounds like he assumes that her rescuer is her lover.
 Conan Drill
A more official confirmation they may have had a relationship was given in the official Detective Conan guidebook Conan Drill. On page 239, there is a diagram of the relationships between various Black Organization members. Gin's feelings towards Shiho were listed as "abnormal attachment" and her feelings for him were "hatred". It also stated they may have had a love affair or relationship and that perhaps Shiho and Vermouth were love rivals.
 See also
- ^ The Pisco case. Gin's predictions were good except for Conan's involvement.
- ^ Manga Volume 24, Files 7-11
- ^ Manga Volume 24, File 7, pgs 1-3: "A Pack of Lies"
- ^ Manga Volume 24, File 7, pg 7: "A Pack of Lies"
- ^ Manga Volume 24, File 7, pg 18: "A Pack of Lies",File 820
- ^ Quote the whole line here
- ^ a b Manga Volume 24, File 11, pg 3: "The White World"
- ^ 異常な執着
- ^ 憎しみ
- ^ 恋愛関係？
- ^ 恋のライバル…? Vermouth and Gin's love relationship arrow was labeled "sexual relations" (肉体関係) so if Gin was in a relationship with Shiho as well, Vermouth would have been love rivals with Shiho over Gin.