You would have to delete your EU eShop account and use CTRtransfer (hacking/homebrew required) to region change your system to J. This would still have a fairly high chance of not working due to Nintendo locking you out of its servers, especially if you use a New 3DS (because many N3DS's come pre-registered to a particular region's servers, even before they're turned on).
Response above seems to be confusing this for the Switch forum.