Tokyo Haneda Int'l to Int'l Connection

It would be on 2 seperate tickets. A zed ticket on either Korean or ANA from Seoul, then a listing on Delta to get home. The flight arrives into HND at 10:15 pm and departs for SEA at 12:30 am. I know if it were on a through ticket I could use the transfer desk but I'm not so sure how that would work with 2 separate listings on 2 airlines. This is of course assuming everything is on time (and I get on the flight for that matter). I'm really trying to squeeze in the DMZ tour in Korea and head straight for the airport after. I'm hoping I don't have to clear customs, and go through the whole checkin and customs process again. Just transfer and go through security to my flight. Has anyone had any experience with this?