In this article discussing the possibility of Girls' Last Tour Season 2, the final chapters of the manga were summarized. Without getting into spoilers myself, I have to say the ending for the manga's story was fitting based on the overall tone of the anime, but if the manga were to be adapted completely I want one change. The anime adaptation should extend the manga's story with original content to give us more details about life in that world.
It's like, seriously, in the anime we get fungus people making mysterious statements and a big info dump in the submarine, but then nothing much after that. It's obvious that WW3 with giant robots happened, but that's all we know. Never mind, it'd be nice to know what exactly happened with grandpa and why their village started fighting.
I know some people don't like anime original content aka filler, but in this case it's a necessity for a second season. Although, arguably they could finish off the story with an OVA episode or two by just focusing on the highlights of the manga's ending. Doubt they'd want to do a movie since the story isn't action-packed, but the entire story could probably be summarized in 1.5 hours.
From there, the story takes a dark turn in Volume 6 as life whittles away at hope as they suffer loss after loss. First, their vehicle, the Kettenkrad, finally breaks down beyond any repair. They memorialize their fallen comrade by turning the vehicle into a water bath in which they drink beer and sing.
Second, they throw away the gun after it becomes too heavy to carry in their packs. Chito’s precious books are next to go into the fire; literally. They even burn Chito’s personal journal except for the map. Yurri also suffers a loss since they eat their canned fish first because it’s so heavy.
Finally, their lantern goes out as they’re ascending a spiral staircase and they’re plunged into darkness. They felt as if they had returned to the darkness from which they came from. But they held hands, reminding themselves that they were still alive and together, feeling as if they were connected to the whole world.
Finally, light from above pierces their dark death march and the staircase opens up to the highest level. There, they find… absolutely nothing. Only snow on an empty plain, some large stones, and the night skies.
As they consider what to do, they look over the landscape below and ponder what it means to be happy. They even have a snowball fight! In the end, they decide to eat their last food and go to sleep, determining to figure out their plans in the morning.
