Attack on Titan season 3's penultimate episode "That Day" breaks down the secret history of Eren Yeager's father, Grisha, and blows the lid off the series' established mythos in the process. Not only does "That Day" reveal the official origin of the Titans, and redefine the entire world of Attack on Titan, it also changes the entire context of the series' first episodes!
As you will see below, Attack on Titan didn't just plunge the dagger into fans' hearts with last night's episode - it twisted the blade around until a bleeding wound was left in every fan who's been with the series since the start:
The backstory of Grisha Yeager reveals the secret history of two civilizations: the nation of Marley and the Eldian Empire. Eldia is revealed to be the home of the Subjects of Ymir, the race of humans that can transform into Titans, while Marley was a conquered nation that eventually rose up to take the power of the special Titans from their Eldian conquerors. The terrible history of the war between Marley and Eldia had many brutal acts of killing involved, and Grisha Yeager has seen some of the worst.
After his sister was sadistically murdered by Marley Public Security Authorities, Grisha was inspired to join the Eldia Restorationists as a young man, fighting to restore the Eldian people to their former greatness, free from Marley oppression. The Restorationists never got the chance, however, as Grisha's young son Zeke turned the group in to the Marley Security Authorities. The Restorationists were given a horrific punishment: The were taken to Paradis Island and brought up to the top of the Wall; there they were transformed into Pure Titans and set loose to roam Paradis Island. That fate was shared by all of Grisha's fellow Restorationist comrades, including his wife (and Zeke's mother) Dina Fritz.
⚠️ Anime Spoilers ⚠️June 17, 2019
As you can see above, the Eldian Restorationists didn't just become any random set of Titans - they were transformed into the Titans that attacked Shinganshina District in Attack on Titan's first two episodes! A rewatch of the series premiere episodes "To You, in 2000 Years: The Fall of Shiganshina Part 1" and "That Day: The Fall of Shiganshina Part 2" confirms that the same Eldian Restorationists transformed by sadistic Marleyan Sergeant Gross are indeed the same Titans who destroy Shinganshina District and wreck Eren Yeagers life. If that wasn't enough of a mind-screw: it turns out that the Titan who killed and ate Eren's mother, Carla, was actually Grisha's first wife, Dina! Before she was transformed, Dina had promised Grisha she would find him wherever he was and they would always be together - but Grisha probably never figured on just what kind of nightmare that promise would become...
Attack on Titan season 3 part 2 is now streaming weekly on Hulu, Funimation and Crunchy Roll.