Maybe it's true that people fetishize past traumas. Korra has spent her entire life with her actions dictated by others, having to fight tooth & nail for the right to make her own choices. And then suddenly, in the City, all those restrictions are gone. The Avatar is just another word. Nobody cares who she is or what she does. As much as Korra enjoys her newfound freedom, it leaves her feeling unmoored. The times she feels most centered, the most herself, are when she's in bed with Hei. He sets the rules, and she either struggles to obey or to break them. Either way, it's a fight that's both comforting and familiar.

He asks her why she's with him, and that's the answer she's not self-aware enough to give. Nobody else will make her fight for control like he does, and nothing else will offer her the hope of little victories, few enough to keep her hungry but frequent enough to keep her motivated. That's what makes their relationship work.