Going to japan again

I have a lot of vacation time this winter, so I decided to go to Japan again.  I'll be there for about 10 days next month.  I'll be flying to Osaka, but I haven't really planned what I'll do yet.  I'm just going because I like Japan and it's easy for me to go there since I live in Korea.  Once I'm back in the US it's a $1000+ plane ticket and a 14 hour flight.  From Seoul it's about 2 hours and I'm paying about $250.