It was a promise. A promise Derek made when Stiles woke up screaming and crying after another crazy nightmare. He promised that one day - when it was all over - they’ll travel to New-York. They won’t tell anyone, well, maybe Stiles’ dad and Scott, but no one else. They’ll pack their things, buy plane tickets and just go. “Boldly go” Stiles joked through sobs and smiled as Derek pulled him closer and continued. He told Stiles that he would show him around the city, take him to bars and restaurants he and Laura had visited years ago. They’d spend a lot of time in Central Park feeding squirrels or just lying on the grass - whatever Stiles would want. And they would live in a tall building, probably in a penthouse with a nice view on Hudson River and The Statue of Liberty. Derek promised that everyday he and Stiles would wake up together in a cozy bed with lots of pillows on it. They would have movie nights, watch Star Wars, Lord of The Rings and Indiana Jones. Everything would be fine, significantly better than it has been. Derek promised and Stiles believed.
One day it was all over. All the bad guys - gone, everyone alive, bruised and battered, but alive. Things are settled back to normal. Well, as normal as possible in Beacon Hills.
Stiles is no more afraid to die. He feels safe and out of danger. Derek is no more afraid to live. He has a whole world in front of him.
When it was over, finally over, Derek kept the promise and Stiles never doubted it.