There has been quite a bit of discussion about zipair in the Japan forum and that they do not have an airside transit desk and only do point to point flights (search the thread for zipair):
https://www.flyertalk.com/forum/japa...dition-59.html
zipair provides a warning on their website about having to enter countries to transit from zipair to other airlines:
For customers transferring via ZIPAIR to a different airline, all travelers must go through immigration upon arrival, pick up your checked baggage, and go through Customs inspection. You may be required to provide mandatory documents for entering the country of transit. If you cannot provide the documents, boarding may be refused. Please prepare all travel documents in advance.
https://www.zipair.net/en/important/60
I'm not sure how far you'll get with a complaint. As you were departing KOR I guess you could start here:
https://www.kca.go.kr/eng/main.do