6 decades books

Bon Taraka was just your average, everyday college student, until the day known as the Event, when Tutorial Towers appeared all across the world. Bon was transported into a tower, but encounterd an error in the Tutorial System. He got trapped in a Boss room and died, over and over again. With each death came new revelations, until one day he killed the Boss and entered the exit portal. On the other side of the portal he found yet another Boss.