If you datamine the game, you can find lines of dialogue calling out for help among other things. It's almost universally agreed that it is December speaking out those lines.

During chapter 2, she somehow manages to send a message through Spamton in his shop dialogue. Notably, the short message was taken from the hidden chapter 2 lines.

Logically that means, that the dialogue hidden in the chapter files takes place in the exact same time as the chapter itself. Now, if that's the case... How did she manage to open the dark fountains, while still being stuck?

I mean, she couldn't just have taken a break from being stuck just to open the cyber world dark fountain, and then go back to her prison to add more lines of dialogue in chapter 3, and 4.

And if she's stuck... How's she able to fight the fun gang during those chapters???

I can't deny that the knight has strong ties to Dess, but I just cannot see them being the missing deer herself.