I remember reading this and it is just as brilliant as when I first read it.
Lily's hints to Sirius, wanting him to look at her, to notice her. It was a game, but a serious one. Naturally, Sirius gives in, what can he do when the girl he loves pleads for him?
But in the end, he knows the truth. Lily belongs to Jmaes, even if she never felt the same way towards James as she did Sirius, it is still wrong to move in on a mates woman and although he did slip up, in the end, Sirius gave up his heart for his mate, his brother! So very touching!
The ending is what I love the most, the love is still there, even though things changed and she married James. Using her own words back at her :) I really loved this!!!