I had this idea pop into my head today and its actually quite odd in one sense and at the very least plausible because of unknown background stories on certain characters.
*My apologies if someone has already posted on this or make a similar topic ETC, I just started reading these forums again after one year or so off and havent looked back to see if anyone has come up with anything similar*
The idea is this: In the series, there has been two character that I just noticed that are similar in a handful of ways. (Again, a lot of this is speculative but thats why in the the theory section )
Mito Uzumaki and Karin... LOLWUT?
Well based off there appearance in the manga, they both have long red-ish hair(Mito, as far as I know, has not appeared in the anime but since she is from the Uzumaki clan, I can at least assume she has red hair)
Both have Pupil-less eyes, I cannot say they both have red eyes but Karin does have red eyes. (Kushina and the Konoha leader didnt have pupil-less eyes, Kunshina's eyes are similar to naruto's own eyes, so I cannot say its a Uzumaki clan trait but its in both there character designs)
Both are sensor types that sense negative emotions, while as far as I know Karin's abilities see the chakra and its based off the feeling she gets from it, good or bad. According to the wiki she had the ability to sense negative emotion due to her control of the nine tail fox. So while I cannot say she didnt have the ability before hand, she did have it, I guess in a similar fashion to Naruto in his nine tail chakra form sensing emotions.
So where am I getting at with all this... Karin, based off character design and her own back story of being a survivor of a small village that was burned to the ground during a war(the Uzumaki clan was destroyed, but I am also sure other clans where destroyed in a similar fashion, so it cannot be use as definitive proof but as a similarity), is one of the last surviving members of the Uzumaki clan.
I believe Kushina mentioned to naruto that since there village was destroyed, that the surviving members scattered to different parts of the world, and probably other clans. But that also gets thrown into question when she is first seen with a distinguishable headband of Kusagakure but you can also say, since Oro was the one who found her, he may have placed her in that village when she appeared in the first chunin exam, when sasuke saved her. So her true village is, at this point, impossible to say.
While this is all speculative, at the very least some of this is based on what I have seen. Its either strictly a design choice by Kishimoto when he designed Karin and gave Mito her appears to be similar to Karin's look.
Or there is another huge, plot hole inducing bit that is going to come up with Naruto and what could be the last of his clan if he meets up with her again at some point in the manga.
So that's what I got, I want to see if anyone else see this and can either agree of disagree with me. Because the more I think about the visible similarities and what is known for sure, its at least in the area of plausible but unlikely.