WARNING: The following contains spoilers for Chapter #135 of Attack on Titan, "The Battle of Heaven and Earth," by Hajime Isayama, Dezi Sienty and Alex Ko Ransom, now available in English from Kodansha.
The Attack on Titan manga is right on the cusp of its long-awaited ending and humanity's remaining heroes are taking things down to the wire. With untold numbers crushed already by Eren's rumbling and his army of Wall Titans showing no signs of slowing down, what remains of the Survey Corps and Marleyan Warriors have engaged in a desperate battle atop his humungous Founding Titan form. In Chapter #135, the summoning of a seemingly endless barrage of former Titan Shifter holders forces them to flee, barely alive, on the back of Falco's winged Jaw Titan...
... All except for one, that is. As Mikasa, Levi, Jean, Connie, Reiner (and possibly Pieck) fly away from Eren with Annie and Gabi, only Armin remains. While it's possible that Falco could swoop back in for another drop-off, the move would be a risky one considering they know what's waiting for them on the Founding Titan's spine. This means that presently, humanity's best hope for survival lies entirely with Armin Alert. And really, this makes perfect sense considering his character arc and what he now knows about Ymir's part in all this. Armin, and no one else in the world right now, might know what needs to be done to defeat Eren.
Armin is currently being held captive in a near-unconscious state. After working out that Ymir, the Founder, is behind the Titan Shifter resurrections, not Eren, the young Commander is dragged away by one of them who starts suffocating him with its tongue. Though his allies are unsure of his status, they surmise that he must be physically in-tact, at least, else his Colossal Titan form would have been unleashed. It's a clever move on Ymir's part, as keeping Armin trussed up like this prevents him from using his two greatest assets -- his huge Titan body and his voice to command his friends.
Or, could it be that Armin is actually being held by Eren? Over the past couple of chapters, we've seen Armin share an exclusive line of communication with Eren that others haven't been privy to -- not even Mikasa. Armin seems to be able to tap into his former friends' psyche, via the Coordinate Point, almost without the two of them consciously reaching out to each other. It's possible that Eren either wants Armin to be spared, or considers him to be the only one actually capable of stopping his horrible plan. If the latter is true, Eren is right to be wary of Armin, Paradis Island's foremost strategist.
Armin began Attack on Titan seeming to fulfill the protagonist's sidekick role pretty comfortably. But as the series progressed, he gradually proved that his astute mind, empathy and fighting spirit were more than enough to match all of Eren's own heroic qualities (and without the shades of emo, to boot). By now, it's become clear that Armin might have been the Naruto to Eren's Sasuke all along: the true hero of the series. As Eren has fallen further and further into darkness, Armin has only shone brighter and brighter, which is why it seems unlikely that he'll be killed off here and now in such unheroic fashion. With only himself, Eren and Ymir left at the center of the battlefield, it appears a standoff is about to go down -- just not one that any onlookers will be able to see.
Near the chapter's end, Armin "wakes up" in darkness with Bertolt, the Colossal Titan's former holder, standing over him in tears. What significance this will have in the next -- and possibly final -- chapter, is any fan's guess, but it seems likely, with Armin having finally put the pieces together about Eren and Ymir's joined wills, that the Coordinate plane is the only stage on which he could meaningfully engage with either of them after all combative efforts so far failing. The time for diplomacy with Eren is fast running out, but Armin might be more open to doing something drastic about Ymir's existence.
As the mother of all Titans, severing her connection to her subjects might be the only thing that could halt this carnage once and for all. After all, while Zeke's plot to end the Eldian race is obviously reprehensibly misguided, cutting off the Nine Titans' spiritual power source is less controversial and, more importantly for him, might spare Armin from having to live with the trauma of killing his childhood friend.