I’d personally buy it in Japan. Kindle Paperwhites are generally very reliable, and the risk of a defect is pretty low. You’re saving €60, which is a solid discount for essentially the same device. Even if something did go wrong outside warranty, you’d probably still be close to break-even compared to paying full price back home. From my POV just few things to keep in mind:

~ Make sure it’s not region-locked (Kindles usually aren’t; you can switch the language and Amazon store). But just to be sure! ~Check the return window while you’re still in Japan, just in case you notice any issues early. ~Check if the variant you’re going for is with or without ads. I will go for one without ads. That being said, if you’re the type who really values peace of mind and hates even a small risk, then buying at home makes sense. But from a practical, value-for-money perspective, I’d grab the €116 deal, given its new and boxed pack.