Our hand gesture prince was wearing a pants with legging from KTZ for SMTOWN III Concert in Seoul.
I know it's pretty old. I think Siwon started to have a habit to wear something strange for his on stage outfit. He was spotted wearing a pants plus the legging from brand KTZ. It's called Church Embroidery Shorts With Printed Legging.
Here's the buy link
It's still available on KTZ official site and the price for this pants is £305.10. What's interesting from this pants is, it's made to order, so when you placed your order, then they will started to make it.