Being an F rank demon and leveling up to become an S rank one.

Markov was born as a pitiful F rank demon. And to make matters worse he's a Hellspawn, one of the weakest demons out there. But still, his best friend Volo inspired him to go traveling through hell and level up his powers to join the S rank demons. But of course it is not that easy as humans have decided it is a nice time to attempt to colonize hell, and with a civil war on the demon's future? Markov may never achieve his dream, but he will certainly try.