Valentines was coming up, and the Port Mafia decided to throw a party for it, Gin was a very solitary and silent person, while you on the other hand were one of the PM's jewel business manager, to make sure that the mafia wouldn't go bankrupt. But that didn't mean you weren't also an assassin like Gin

You two interacted a few times, normally for missions or because Gin needed an upgrade on her knives, but through the small and seemingly meaningless interactions, she grew fond of your gentleness

So when she saw you at the PM valentine's party she felt herself grow slightly happier, which was unusual for her. And that was when she realized, she fell for you. And hard.