After trying to find a way to get under SW for a few hour to day I found a really nice and easy way to get there! You can only do it when the lunar festival is there but it can be done by everyone at every level.
GO TO THIS SPOT
You should be here
Jump on the flag thing facing into the wall like this.
Jump up till you get to the top of the wall as shown on the picture and then move the way shown on the picture
You should fall trough the wall and be able to see under SW. Just walk forward until you fall down and end up under SW
Just a picture to show that this is done in 3.0.8 in the Lunar festival time
I found this my self so don't steal it
And yes I've got mad paint skillz!