Attack on Titan episode 81 finally brings back Annie Leonhart - and it's all thanks to Eren Jaeger. How does Annie's long-awaited return happen?

How does Eren Jaeger bring about Annie's long-awaited return in Attack on Titan episode 81? The days when Paradis Island's biggest worry was a single Titan-shifter hiding within the walls seem awfully far away, but that was the situation last time Annie Leonhart appeared in Attack on Titan. The first of Marley's Warrior Candidate infiltrators to get rumbled by the Survey Corps, Annie's secret was uncovered by Armin Arlert after the mysterious Female Titan terrorized Squad Levi in pursuit of Eren Jaeger. Defeated by Eren's Attack Titan and the Survey Corps' sublime teamwork, Annie encased herself in Titan hardening to avoid being questioned or tortured. Her crystallized body has been collecting dust in a basement ever since.

That ends with Attack on Titan episode 81, "Thaw," which foreshadows Annie's return in its very title. Having sweet-talked Ymir Fritz into giving him full control of the Coordinate, Eren has transformed into the monstrous Founding Titan, attaining mastery over all Eldians. Eren's first order of business is triggering the apocalypse, unleashing every single Titan housed inside Walls Maria, Rose and Sina. Able to influence all Subjects of Ymir, Eren then psychically addresses his entire race, revealing intentions to kill everyone whose zip code falls outside of Paradis Island. Attack on Titan episode 81's final scene shows how, in the melee of Eren's wall-breaking, Annie Leonhart finally emerged from her cocoon, 3 seasons and approximately 4 in-universe years since turning herself into the mother of all paperweights. Laying in a pool of melted Titan juice, how is Annie freed, and why has she returned now?

As the ever-alert Armin Arlert deduces, Annie's release is a direct consequence of Eren's order to bring down the three Paradis Island walls. Although Titan-shifter hardening abilities often look different from Titan to Titan, it's the same technique. Reiner's Armored Titan shell, Eren's steel blue knuckledusters, the Female Titan's crystallization - all three seem unique to the eye, but all three are examples of a Titan's ability to create diamond-hard coating. The Wall Titans represent another example of the Titan hardening technique - albeit on a scale only the Founding Titan is capable of. Over a century before Attack on Titan's current era, King Fritz used the Founder to create and crystallize every single Wall Titan, giving the three circular feats of architecture their structural strength.

In order for Eren to release Paradis Island's Wall Titan army, he uses the Founder's power to undo their hardening, waking up the sleeping giants from their century-long slumber. The actual order Eren gives, however, is to release all Titan hardening. As Reiner points out, this results in him losing the Armored Titan's protection completely, and because Annie's crystal is made of exactly the same stuff, she's affected too. Annie had no involvement in her release, and would've been just as surprised as anyone to find herself laying soggy on the floor, 4 years after last tasting fresh air.

Just as important as how Eren released Annie is whether he actually meant to. Is Eren still getting to grips with the Founding Titan's power, and made the rookie mistake of not specifying which crystallization he wanted undone? Or is there a deeper purpose to setting Annie free? Since Eren is in no mood for chatting, Attack on Titan gives no concrete answer. But we know Eren's overarching motivation is protecting his friends on Paradis Island, whatever the cost. And as proven by his brutal verbal and physical beat-down in Attack on Titan season 4, part 1's restaurant scene, Eren also knows Armin has developed romantic feelings for Annie, visiting her crystal over the past 4 years. Since Eren really does care about his friends, maybe releasing Annie was his way of apologizing to Armin for the insults and injuries - a chance of happiness with the girl he's grown to love, as a means of saying sorry for all the punching.

Switching from Eren Jaeger's perspective to Hajime Isayama's (Attack on Titan author) Annie's return is easier to understand. Her crystallized form remained an unsolved plot point heading into Attack on Titan's finale, and Eren's Founding Titan power provided the best opportunity to solve it. Attack on Titan's final episodes are also revisiting what fans originally fell in love with. Episode 81's Survey Corps vs. Titans battle is a pure throwback to season 1, for instance. By the same ticket, Attack on Titan's ending would not have been complete without Annie Leonhart's return.

More: Ymir Fritz's Backstory Explains 7 Attack On Titan Mysteries

Attack on Titan season 4 streams Sundays on Funimation, Crunchyroll, and Hulu.