When I was talking about the kiss of freedom in my thread on Eremika kiss in their reunion, months ago, I realise now that the kiss they shared is deeply the kiss of freedom.

Let me explain to you my view

In chapter 50, when Mikasa made an indirect confession to Eren, it was so impactful that Eren regenerated his hands very quickly and the strength he gave off was breathtaking, whereas he was completely devastated seconds before

In 138, Eren has his eyes closed, he doesn't want to see his actions so much that he prefers to leave them like this. He feels completely bad too, but his guardian angel has arrived, he opened his eyes little by little, &, you can feel peace in his eyes, with a slight smile

Mikasa knows very well what she is doing, if she was going to kill him, which was not even mentioned for her case in the chapter, in my opinion she would have kissed him first and then decapitated him for good

But first she wanted to free him from the spine, from the skeleton, because there is nothing more necessary as a first step to free him, then she kisses him and he responds to her kiss. The same situation as in chapter 50 can happen, without Ymir even intervening.

What does the catchphrase say? : Goodbye to the boy who was looking for freedom! That's fine, he doesn't need to look for it anymore because a light has arrived and true freedom has already been found, a new beginning for him, thanks to Mikasa!

The love she gives him through the kiss can give him back the desire to live and regenerate himself!!! In the same way that Mikasa's simple words allowed him to regenerate very quickly in chapter 50, and when he finally has his whole body, let's imagine his motivation?

It will be powerful to save the others bc they are indeed in difficulty, we come to the sentence: If you want to save Mikasa, Armin, and the others, you must master this power. The time has finally come to understand the meaning of this sentence bc they are indeed all in danger

and only he can save them by perfectly controlling this power as well as with Ymir's help.
In case the kiss has no impact on regeneration, Ymir would therefore give her power to Mikasa or help him to reconstitute his body

but it is undeniable that he will make his return. Chapter 139 is the chapter of Eren.
HE WILL PUT AN END TO THIS WORLD (path)
HE WILL END THIS 2000 YEARS HISTORY OF TITAN (goodbye curse-kun) & Ymir will go at peace

ATTACK TITAN RETURN LET’S GOOOOO LET’S GOOOOO