The ending of Attack on Titan Manga - Chapter #139 explained
You can read the scan of Chapter 139 on ReadSNK. Of course I invite you to buy the manga, it is worth it, and you will support the creator!
So it came the day when even Attack on Titan reached its ending. The masterpiece manga that entertained a lot of people.
The ending was quite surprising though, and many aspects are still hard to comprehend.
Explanation
Here is what happened in chapter 139.
Armin and Eren are talking inside the "paths", which is a kind of "parallel universe" where the time stands still, it is a place created by Ymir. Eren has the Founder Titan so he has a kind of control over this place.
Eren explains to Armin that he killed 80% of the inhabitants of the planet just so he would be considered the bad guys, while Armin and Mikasa would be considered the heroes that saved humanity.
The hate speech towards Eren and Mikasa was planned to keep them away and make Mikasa hate Eren.
We discover that Eren saw the future at the awarding ceremony, probably when he touched Historia's hand. In a scene, Eren confesses he had decided in that moment the actions he would take in the future.
Basically Eren chose the "path" that lead do Mikasa. Ymir was in love with King Fritz and she has been a slave of this love for 2000 years. Apparently she recognized Mikasa as the right person to help her reach her freedom.
Eren just followed this path, explaining that he saved Berthold from being eaten by Dina's titan, in exchange he sent Dina to eat his (Eren's) mom. We can think that he did so in order to put the Eren from the past in the condition of hating titans. This point of the plot if very arguable though.
We see Eren saying that he didn't really want Mikasa to forget him. He wants her to live a happy life but not with another guy. He wants to avoid death and live with Mikasa and Armin forever.
Ymir's curse has been removed when Mikasa killed Eren and the Founder. Apparently Ymir is dead now too. For this reason, the titans are back in their human form.
In the ending part, we have a fast forward where we see the survivors of Paradis dressed as diplomats on Historia's behalf. They have to discuss the peace between Paradis and the world.
Meanwhile Historia gave birth to a baby and she keeps being the queen of the Eldians.
Mikasa decides she will bury Eren under the tree where the story began, when she tells him "See you later, Eren" in the first chapter of the manga. She'd like to see Eren again and here comes a seagull that tries to take her scarf away from her neck. Because of this, she understands Eren is still "near" her, in her heart.
My opinions
To be very honest, I was pretty much disappointed for this final chapter. I had lot of expectations about an epic ending with more plot twists, like I was used to see in this masterpiece... but the ending was too simple, too normal, nothing special. Chapter 138 blasted me with the scene of Mikasa decapitating Eren... But number 139, I don't know, it left me totally indifferent. It was a "good" ending for the main characters, but many people still died, so it was kinda sad. It was not too sad though, because the titans get reverted to humans and the only sad death was Eren's one. A lot of questions still remain open and unanswered. Of course we can build many hypothesis.
The main feeling for me was that this ending was rushed. Like, Isayama maybe was really tiredand didn't want to put too much effort in the ending. Probably the manga was pushed to the limits for businesses reasons, I don't know.
I was not expecting a good ending, on the opposite I expected Mikasa to suicide or die for Eren, and Armin to try and save them by talking with Ymir and trying to accomplish one of his genious plans, failing in the process because Ymir would have refused to help him. But no, Eren behaved like the most classic cliches, the good guy turning into evil only to be guilty in front of the world. He wanted to save his friends but he still killed 80% of the population, he hurt Mikasa's feelings, he lost her forever, and yea this is kinda sad but was quite expected. This masterpiece was full of plot twists and it would have been nice to see a dramatic final unexpected twist.
It was a decent ending, I accept it, but could have been much better in my opinion.