Surviving as an SSS-Class Alternate Character

It is the year 203X, and Junwoo is a pro at "Over the Fantasy," a virtual reality game. One of his secret strategies is to keep an alternate character for extra inventory space to store his main characters' shiny items. But one unlucky day, a server error traps him inside the game—and as Dio, the classless alternate character! The situation seems dire, but he has an inventory teeming with SSS-class items to help him survive in this fantasy world. They should be enough to keep him going... Right?