Theory time!

amayaokami:

According to this, both bloodlines were persecuted and couldn’t remain in the cities. Mikasa’s parent’s moved to the mountains to avoid oppression, but Levi’s mother sought safety in the underground, meaning it’s possible there are members of both bloodlines hiding out down there.

Why does this matter? Because Levi is from the underground. Levi was a thug that knew those streets very well and likely knew a lot of people. I used to believe Levi took an interest in Mikasa because she was an Ackerman, but now that the theory was debunked (due to him not knowing squat about his connection to the family), I think Levi might’ve met someone from the Asian bloodline instead. 

That could be yet another possible reason why he stares at Mikasa and behaves…peculiar toward her–her rare features may remind him of someone he used to know and/or he knows some info about the bloodline (nothing crucial, but I’ll explain how it might help them learn more about the bloodline in the long run). 

Let’s assume for a moment that Levi had in fact met someone from the Asian bloodline. What if Mikasa reveals the brand her mother gave her and Levi recognizes the mark?

The brand seems to be exclusive to Mikasa’s family, so if Levi ever met someone with the same marking, it’s safe to say they were related to Mikasa. 

If Levi did met a member of her family, he might’ve gained some general knowledge about the bloodline during his time in the underground. He might not know all the details, but he might’ve known all along that the Asian’s are in danger–this might explain why he’s “very concerned about” Mikasa:

Levi’s concern for Eren is self-explanatory, but his concern for Mikasa always puzzled me. I always wondered why he wouldn’t be concerned for someone like Hanji; someone he knew longer and was closer to, not a new recruit he had no personal or work experience with (at the time).

When Levi realized Mikasa was the same girl from the trial, his entire deposition changed drastically and he went from believing Eren was dead to trusting her that he was alive. Why does he treat her so differently compared to the others? Why is he concerned about someone he’s not even personally close to/isn’t obligated to protect like Eren? Why does he give her thoughtful, yet ambiguous expressions so often?  Sure, it could be due to their similarities and Levi recognizing her strength, but he behaved this way before he even knew about her abilities or saw her in action, before he knew how alike they were. He acted this way toward her from the moment they met and there needs to be a solid reason why.

Levi’s interest, concern, and sympathy for Mikasa would make more sense if you assume Levi knows something about her bloodline, or once knew someone who shared her rare features.

If this is the case, he probably isn’t bringing this up with her yet because like I said, he might not know much. Either he simply met someone of Asian descent and/or he heard about their oppression. Also, he might not know if it’s related to her or not; at the moment he would have no way of knowing if someone he met in the underground had any direct connection to Mikasa. However, if he happens to recognize the brand on her wrist, he would realize that Mikasa’s not simply from a rare bloodline, but her family is apart of an important clan that he may have heard about before. As of right now I strongly suspect that he met someone from her mother’s side that has the same brand, and he will piece together a connection if and when he sees it.

Think about it: the brand must be important. Why else would Mikasa’s family put this mark on their children generation after generation? Even Mikasa’s mother said the brand MUST be passed on and she straight up told her she will do the same with her children. I don’t think it’s a meaningless tradition. I think it represents something. The Asian’s (and Ackerman’s) are the only ones with ancestors who actually remember what happened after humanity undergone a massive mindwipe. Perhaps the brand symbolizes the true history. They couldn’t keep that information stored in books–books about the outside world/time before the walls is illegal and any written documents about it would be destroyed if found, so they might’ve figured the best and safest way to pass down this information was by permanently marking their skin. 

Perhaps Mikasa’s mother planned to tell her about the true meaning of her brand when she was old enough to understand, but now that she’s gone the only way she’ll learn the importance of the mark and her mothers family is by meeting a relative–a relative that I believe Levi might’ve met already.. Assuming this person is still alive and still lives in the underground, he could possibly bring this relative and Mikasa together so they all finally learn the truth.