The rain over Paradis had not stopped for three days. It fell in grey, weeping sheets over the walls that were no longer walls—over the districts that had become tombs, over the memory of a boy who had once stared at the clouds and called them free.
The series also explores the theme of survival, as the characters are forced to fight for their lives in a world that is hostile and unforgiving. The walls that separate the humans from the Titans can be seen as a symbol of the boundaries that humans create to protect themselves from the outside world, and the consequences of becoming complacent and isolated. Shingeki no Kyojin- The Final Season Part 2
Millions of Colossal Titans, previously asleep within the walls, opened their glowing eyes. They stepped forward in unison, their massive feet shaking the very foundations of the earth. The rain over Paradis had not stopped for three days