Broke brothers Kanade and Kaname Nakata might have found their way out of poverty: a mysterious app called "Six" that offers bounties to whoever can slay monsters known as "Worlds." But juggling school, rent, and building-sized spiders isn't as rewarding as all those zeroes might make it look! As they meet more of the app's users, they come ever closer to understanding the secrets of "Six"...But will they fall into inescapable debt from fumbling their missions first?