Fujiko Mine (峰 不二子, Mine Fujiko) is a professional criminal, burglar and confidence trickster. In The Castle of Cagliostro Fujiko states that she and Lupin had been lovers, but also that she ended the relationship.
She routinely makes deals with Koichi Zenigata or Lupin's current enemy in an attempt to gain freedom or loot, which causes Jigen and Goemon to distrust her, since they know that she will obviously double-cross them in a heist to claim what they're after for herself. While Lupin normally can outsmart Fujiko, she can make off with some or all of his loot on occasion.