All Nippon Airways Mileage Club - Practical check-in question

I am flying domestic from Haneda tomorrow at 06:35, and was wondering what time ANA opens the check-in counters. When I flew JAL this early they only opened at 5:30, and at that time of the day there is no point in being there a minute earlier than necessary.

The booking did say I could wait with payment until 20 minutes before depature, I guess check-in as well. Or?

They open at 5:15.

NH domestic (high density) configured widebodies begin boarding 20 min before departure, narrowbodies, 15 - unlike people here in the US, the Japanese don't drag on a ton of carry on luggage. Security is a breeze even at that time in the morning, 10 minutes tops. That being said, I wouldn't cut it too close.

Is there a priority line for security?

Yes, two -- near desks 13 and 39. The one near desk 13 is directly connected to one of the lounges.