What shocks me is that JAL is pretty clear about carry on requirements - https://www.jal.co.jp/jp/en/inter/baggage/inflight/ - 10KGs combined for your carry on an personal item. Agent kept insisting that carry on could only be 7KGs regardless if I had personal item or not. Come to boarding time you should have seen the size of some of the carry ons - definitely outside the limits.

But I did learn something - that if you check in online you can actually bypass the check in counters with mobile boarding passes entirely to avoid this problem as that is where a lot of new agents are stationed. Good tip from my Japanese friends who always try and avoid the check in counters now due to uneven service levels.