AEON Gold Visa
Transaction date: 5/10/15
Amount: JPY 1300
Amount charged: MYR 47.81
Actual rate: 3.677

CIMB World Mastercard
Transaction date: 5/10/15
Amount: JPY 1984
Amount charged: MYR 70.80
Actual rate: 3.569

AEON Gold Visa
Transaction date: 5/10/15
Amount: JPY 1029
Amount charged: MYR 37.84
Actual rate: 3.677

CIMB VISA Signature
Transaction date: 6/10/15
Amount: JPY 1360
Amount charged: MYR 49.89
Actual rate: 3.668

AEON Gold Visa
Transaction date: 7/10/15
Amount: JPY 662
Amount charged: MYR 24.35
Actual rate: 3.678

AEON Gold Visa
Transaction date: 7/10/15
Amount: JPY 1444
Amount charged: MYR 53.10
Actual rate: 3.678

CIMB VISA Signature
Transaction date: 10/10/15
Amount: JPY 17672
Amount charged: MYR 633.25
Actual rate: 3.583

Looks like CIMB is better to use in Japan than AEON, despite AEON hailing from that part of the world. CIMB World Mastercard transaction was posted 10 days after the purchase, which was too late for me to make a comparison otherwise would have used it all the way :'(