A place to leave luggage in Seoul for 48 hours?!

I'm thinking of going to the world dj festival in Seoul on 26th - 28th May. However this will be on my way home as my flight out of Seoul is on May 29th. I would need somewhere to store my luggage for around 48 hours, does anyone know anywhere I can do this? I know the lockers at the train stations have time limits, mostly up to 24 hours!

 

thanks!