Under current technology, that speed is very much impossible. Even if your internet connection was magically instant, there are still more bottlenecks in the way.
A high end NVMe SSD can write up to 12 GB/s. So even if we cheat and say the download is a highly compressible zip bomb that downloads instantly, it’s going to take about 42 seconds just to decompress and write it to the drive.
The DS version of Ni no Kuni included a physical spellbook you’re meant to consult. JP-only, but the fantranslation made it into a PDF.