Setsura would go that far to keep Akito safe. At first, Yang thought he was overthinking things. But the more he thought about it, the more it adds up. The main reason why Setsura doesn't want to regain her memories. Why she chose to forget is to protect Akito.
Whatever secret she discovered will most-likely put Akito in danger. She loves him that much? No, even if she does love him that much. Yang could still break their relationship apart. Will she be able to return to Akito, after entering a relationship with him? The answer is no.
If he does it with her, then Setsura won't be able to turn back. The problem is, whenever he thinks of doing it. He ends up stopping. Aaah, what is with this stupid dilemma? He sounds like an idiot..
