I've done HND-ICN-FRA/DXB before. Indeed it can be a bit of a slog timing-wise, but luckily the KE lounge has a sleeper pod I can use during the layover to catch up in sleep.

The reverse routing isn't as bad. I've done SFO/LAX/FRA/CDG-ICN-HND with 3-4 hours layover at ICN.

KE used to offer their HND-ICN flight at 6:20am until the mid-2010s; meanwhile, OZ offered a 6:00am departure until sometime in summer 2023. I actually flew it in June. Not sure why it was moved to 2:00am though.