The fanfiction, if I remember correctly, was by an author called "Ro". The Gundam pilots had lost the war, and Wufei had been given to Treize as some kind of token, to demonstrate that they would not fight again. Lady Une was the evil character in this fic, she had "trained" Wufei to completely obey her orders (which were to please Treize in everything he wanted) and as a result Wufei was terrified of women, though he could somehow cope with Treize's daughter, Mariameia.
Zechs was in the fic too, he and Treize gave Wufei as many gifts as years he had for his birthday (I think it included a piercing and a new haircut).
...so...anyone recognise it? ;_______;