Yusuf and Eames are exes who broke up because Eames was more into D/s than Yusuf. Now Eames is after Arthur, who's matter-of-fact about his taste for domination, and seeing that, Yusuf's realizing that it's not so much that he's not into D/s as that he's submissive too.
Yusuf/Eames, Arthur/Eames, possible Arthur/Eames/Yusuf, D/s