At the beginning of the chaos, a major event happened in the fairy world that had existed for thousands of years. The demonic realm, which had been suppressed by the fairy world for thousands of years, began to make moves, and Fairy Oak was involved in this entanglement, so... Everything is unknown.
Have you ever heard of similar space-time? It is similar to our space-time, but different from it. Like two intersecting lines, they may intersect at one point or they may go further and further apart. It's not like our time and space. The warmth we were reluctant to let go of in those years can at least leave no regrets there. My self in another time and space remembers happiness, remembers loving him, and remembers being happy on my behalf.