According to Amazon Japan, the digital download of Xenoblade Chronicles will eat up 3.6GB of your New 3DS Micro-SD card. Given the bundled memory card weighs in at only 4GB, it may be time to upgrade.
It's the largest game download to date for the handheld. Super Smash Bros. for Nintendo 3DS weighed in at 1.2GB, Monster Hunter 4 Ultimate 2.6GB and current champ Bravely Default took up 3.2GB.