Note: Just reading this poem might be hard to understand, so here's a short explaination for ya.
Yami is thinking about his family and how much his misses them. And the door he's reffering to is the door that they mention him going through at the end of the Cerimonial Battle mini season of Yu-Gi-Oh!. Also please note that this poem takes place way before Yami actuallyenters the door; this is just what's on Yami's mind as he waits...
The Door
I'm waiting for the moment that it all ends
Waiting for time to halt
Watch as around me as the people break and bend
Crying as I think of it all
My family, what was life like, what it is for
All I want is to see them again
Waiting for me behind that door
Fate is a cruel serpent
Constricting around my core
With each breath I take I feel it tighten
Detaining me from reaching that door
Happiness is just out of my grasp
Just beyond my arms distance
I just want to get back
To the place of my first existence
Is it to much to implore
To want the key to open that door
I've changed my mind
I've mended my ways
Why is destiny so unkind
Am I to wander the rest of my days
At the tip of there touch
Just out of their wings
I do know this much
If I put aside everything
And close my eyes
On the shadowy light that plays upon them
I see the figures I recognize
But as I open them again
My family disappears as so many times before
But at least I know they too are waiting
Behind that closed door…