The first story is about Spike finding Anya.
She's the perfect sidekick (not only because she shares a number of scenes with Spike but) because they are both opposite and alike at the same time.
Anya's odd, blunt-yet-bubbly personality serves as an interesting contrast to Spike's sarcastic, dry humor. It gives them interesting interactions. While she's playful with him, he's serious with her. They also have opposite talents, Anyas good with money, magic, and housework whereas Spike is a man of action. At their core, however, Spike and Anya are motivated by the same thing—love. Love is the one thing that has defined and redefined them throughout the years. Although they put on a tough front, they are both softies at heart.
Of all the characters, Anya seems to have an understanding of Spike that the others lack whether it be 100+ years of experience or the feeling of unrequited love.