Not sure about difference between 2016 and 2018 model but if you buy the kindle yourself, do note that Amazon USA has very good service and warranty support. If your kindle is spoilt (touch wood), you can contact Amazon USA for help. A few years ago my kindle screen was spoilt and i contacted their CS. Sent back the old kindle and they sent me a new one (dunno refurbished or not... it looks new ) and reimbursed me my shipping charges. I don't think you are able to do that if you buy from Amazon Japan unless you know the language?
Thank you tofubean! After your explanation I have the impulse to purchase 1 immediately!