First time poster here hopng readers can clarify something. Here's my situation--
I'm flying Fukuoka (Japan) to Seoul-Incheon on Korean Airlines. 90 minutes after the scheduled arrival at Incheon, I'm scheduled to fly Turkish Airlines, Seoul-Istanbul.

Now, here's the rub. The two tickets are separate tickets. I bought them at an online agency. I thought since it was under the 'minimum international transfer' time limit that it would be OK, I'd be protected etc. but, obviously, separate tickets are different from a transfer on the same itinery (or with the same, or related, airline). Ouch. I know.

But,
I will have no checked in baggage, only hand bagage.
I will have checked in online for the Turkish Airlines flight and print up my boarding pass in advance.

So, can I not just go through the transfer desk at Incheon after arriving (OK timewise) or MUST I go through immigration into Korea and then all the way to the Turkish Airlines check-in counter (which, of course, closes 1 hr before departure, giving me only 30 minutes from my arrival at Incheon)? The latter puts me at great great risk of missing the check in and even foreiting a huge ticket (family of three).

Help.