[Firebird]

Ok, just to answer my own question:
It was absolutly no Problem to get into Korea without an onward ticket!

However going back to Japan without one seems to be impossible (as some here mentionend). I have asked the guys at the ferry port and they said that for Korea it doesnt matter and if you want to be sure, a reservation for a ticket will be enought (you can still cancel/change that later). They said however that this is not possible for Japan, so be aware!

The Forum for Korea posted by komitsuki is crap (every post is spam, seems to have very few active members) so if anyone know another forum please let me know!

Cheers