SPOILER ALERT: the following article contains massive spoilers, including the ending. If you have not yet seen the movie, proceed at your own risk, or better, come back to this article later!
SPOILERS AHEAD
Digimon Adventure: Last Evolution Kizuna Plot Summary and Synopsis
The team discovers that when they grow up, their relationship with their Digimon will come closer to an end. They realize that the more they fight, the faster their bond breaks and the time to choose is approaching fast.
Source: Wikipedia (CC BY-SA 3.0).