It is not a single account, each character is an individual account, it is meant for those who want to skip the rerolling process but still want a top tier character.
Looking to sell some fresh unlinked, Final Fantasy: Brave Exvius accounts for cheap. After payment just send me the Facebook info you want it linked to and it's done. If you're interested please send me a PM and we can work something out. I will be updating this post periodically with more units...