I thought the ending of the GLT manga was fairly conclusive. Absolute Girl's Last Tour spoiler, don't look here unless you have read the entire manga: They get to the top, find nothing but a large block and after losing everything in trying to complete the journey they then die in their sleep.
Been a while since I read it, yes that makes sense, I guess I was hoping for more? I dunno. The material the anime covered was great though.