I totally agree with you, CTS-KIX is less frequent, it would be a headache if you miss your flight. You would be fine if it is a CTS-HND route.

My outbound to CTS from HND was a Yokoso Japan ticket, first domestic flight in Japan since I was 14 (and on the same route!), when I arrived at the airport at T-2Hours and requested to be put on an earlier flight, they checked the seat availability and said it was ok. so I didn't sense that I've arrived way too early.

Only until I was on my way back to UK, I arrived at 6.10 worrying that I am late for check-in, only to be in shock that the terminal is still dark and not officially opened yet, found my way up to the departure level (had to use the lift, as escalators wasn't switched on), to see some 200+ passengers queuing in front of JAL's desk. (mostly group tour passengers I believe). Got dozens of passengers staring at me when I started queuing in front of JGC desk.

Check-in agents started to come out around 6.27am, when the clock strikes 6.30am lights started to switch on, all agents bow to passengers at exactly the same time to thank passengers for their custom.(I was raised outside Japan, so even till today, I'm still excited when I see these kind of things) My through check-in was done in less then 5 minutes (including asking them to re-assign me to Y bulk head on the long-haul). I got turned away at the dedicated check-in counter as it was "too early"

Returned at the dedicated security lane at 7am, the check-in queue had cleared up...walked pass ordinary security lane to see less than 5 people were queuing.

After this trip, I swear I am never ever going to arrive earlier then T-60minutes at a Japanese domestic terminal. Unless I want to do shopping

Spent an extra ￥12000 on taxi which is totally not necessary, could have taken the train