I posted this in the discussion thread, but this might be a better place:
How does Future Lucy still exist if the Present Lucy's future has been altered completely?
That's something I just can't understand. It's one big paradox.
If the Present Lucy and her friends succeeded in saving everyone and sending the dragons and future rogue back, that means the Lucy from the future never existed because the Present Lucy would never end up like her.
But the Present Lucy only succeeded because Future Lucy assisted her... But now that Present Lucy is going to have a different future, then Future Lucy is no more...
Can someone help me out please?
This is a little complicated. There are two 'types' of settings for time travel
Type 1: There is only one timeline. So a choice made in the present will only result in one future happening out of several possibilities. Consequently, if someone time-travels back from the future to the present and makes a different choice from what led to their future, the original future will be erased and a new one created in its place. Meanwhile the person from the original future who travelled back will be erased as their future no longer exists.
Type 2: There are multiple timelines. Choices made in the present lead to different futures that exist parallel to each other, like multiple branches growing from a tree trunk. For example if someone shoots me, there can be one future where I died and another where I survived. Both exist, and both have different versions of the world: One where I still live and another where I died and everything happened without me.
In such a scenario, if someone from one future travels to the present and makes a different choice from what led to their future, a new future will be created(like a new branch of the tree) but the original future(other branch) will still exist. So the person who came from that future will still exist and when he/she returns, he/she will return to their original future and not the new one created.
Hiro Mashima has basically chosen Type 2. Read it a couple times and it'll make sense. Another example of this is 'Future Trunks' from Dragonball Z.
BTW, as Future Lucy's old post-apocalyptic future still exists, she did not 'return' there. She died and met other dead members of the Fairy Tail from her future. That's why she appeared in a grassy plain and the faces of her fellow Fairy Tail members aren't shown. And if you look carefully you'll see Levy(The one person from her future who was confirmed to be alive) isn't among them.