As soon as you went out of a start door, a lot of appearing boxes will fall.
Go through in a hurry.
Climb a ladder on the far right and then move toward the left.
You can see a row of vanishing ladders on your left.
Run through at a breath.
On the left edge there are a vanishing wooden box and a ladder.
Climb it and go up to the upper.
Then arrange wooden boxes well and get over the discontinuous up and down route made by bricks.
There is a goal door ahead, but you have to climb a ladder and go to the left in order to get a key.