Kingdom hearts has that ability to get you to connect and reconnect to characters in an instant. I too, have post game depression. Its a real thing! You get random spouts and dread once you remember a character, like missing an old friend that you have no means of contacting. Especially after Kh3 it becomes more out there. We as a fandom have to pull through together with it, and once the games end then thats when we have to stick together the most. Encourage yourself and your friends to sit down and talk about the game, maybe find some funny clips or comics or memes about it. Switch your perspective on how you look at the game. Instead of seeing it as an end, think of it as another chapter in a story. It helps keep your mind off things, it really helps.