Based off this song

[There should be a GIF or video here. Update the app now to see it.]

Basically the storyline is that

Dream is the girl

Passive Nightmare is the boy

Blueberry and Cross and planning to kill Dream, because by mistake he killed their lovers in battle, Error and Ink

You are a servant who can secretly turn into a small bird at will, or you can be a servant of Blueberry/Ink, you happen to see everything

...unfortunately, you cannot save Nightmare

Not yet at least.