Just saw this on my Instagram feed!
Take a photo of a MUJI product and post to your instagram and then just show your post when you pay at the counter and they will discount 10%.
Only condition i can see is it's only at their Sydney store, they won't allow discount on already discounted items (pretty standard) and they won't let you order furniture from Japan with the discount (kinda sucks).
Still… not too bad if you wanna buy some things they never seem to discount like the bean bag or new fashion items.
They also have a competition running on Facebook which I posted in the competition section - worth a look.
EDIT: For those wondering, this is some information about MUJI: http://www.muji.com/au/about/
What's a Muji? SOunds like Xiaomi products?