WARNING: The following contains spoilers for Season 4, Episode 10 of Attack on Titan, "A Sound Argument," now streaming on Crunchyroll, Funimation, Amazon Prime and Hulu.
The fourth season of Attack on Titan continues to be the most revelatory in the anime's history -- unsurprisingly considering it's also the last in the anime's history. In-line with this trend, Episode 10, "A Sound Argument" shines a spotlight on Mikasa's previously unknown backstory, revealing that one of the series' most powerful heroes has an even more illustrious standing in the world than her impressive military record alone garners her.
As much as Eren Jaeger is the driving force behind much of Attack on Titan's story, the characters around him are hardly insignificant. Among Paradis Island's finest, Commanders Erwin Smith and Hange Zoe are firm fan-favorites, but few can give the Attack Titan's wielder a run for his money like the Ackermans: Mikasa and Levi. On an island of problematic homogeny, the Ackermans are even more unique than the other Eldians around them, a race that possesses the ability to transform into Titans. The endangered clan grants its members enhanced physical abilities, essentially making them super-soldiers, as well as speculated immunity to the Titan curse. But Episode 10 of Season 4 makes it clear that Mikasa is even more special still, giving her an interesting edge over her distant relative, Levi, and everyone else on the Island.
The revelation comes about via a flashback that took place a couple of years before Season 4's start, to when the Azumabito family visited Paradis Island. As descendants of the Shogun clan from the nation of Hizaru (Attack on Titan's stand-in for Japan), the family is not only prominent emissaries for their country but, unlike the rest of the world, harbor sympathy for Eldians, hence their covert partnership with Zeke (Paradis Island's exclusive resources are also a major motivator). Their main representative, Kiyomi, tells Paradis' military leaders that her people once formed an alliance with the Island at the end of the Great Titan War. In fact, one of their own became close with King Karl Fritz, regularly visiting the monarch until he became accidentally swept up in Eldia's move to the Island.
After the King used the Founding Titan to erase the memories of his subjects, that unnamed man from Hizaru was able to retain his due to his different bloodline. He formed his own clan and united with the Ackermans against the government, leading to them both being ostracized and hunted to near extinction. Mikasa and Levi are currently the only members of either family known to exist on the Island still.
As proof of her word -- that Mikasa is indeed the lone Azumabito on Paradis -- Kiyomi points to a unique mark on Mikasa's wrist, which she's kept hidden from everyone but Eren, stating that the brand means she's Hizaru royalty. This excites Queen Historia, in particular, who has first-hand knowledge of what it's like to be a secret princess.
Though learning about her heritage hasn't noticeably changed Mikasa much in the present, for viewers, it finally solidifies why her parents were killed when she was a child. With an Ackerman father and an Azumabito mother, Mikasa's family were doubly at risk of persecution; Mikasa even more so as the product of two outcasted clans joining together. Her strong attachment to Eren is also even more understandable in this light. He not only saved her from meeting her parents' fate but his family also welcomed her into their home when others on the Island would have shown her nothing but coldness -- or worse.
But the Eren of today is a far cry from the boy Mikasa grew up with, or even the young adult who told her and all of their friends not long before Season 4's start that they mean more to him than anything else in the world. Should the current divide between the two adoptive siblings continue to grow, it's possible Mikasa's newfound understanding of her place in the wider world might offer her a window of escape. If she can no longer call Paradis Island home, she'd be more than welcomed in her ancestral one.