The skeleton is too invincible; I leveled up with the school beauty!

"I transmigrated into an F-rank skeleton soldier?! And I even got a contract with the school beauty?!" My name is Xu Nuo, and I've actually transmigrated into the weakest skeleton in another world! Looking at the stunningly beautiful school beauty with red, tear-filled eyes in front of me, my bone hands are trembling. Everyone else who transmigrates becomes an overpowered protagonist, so why am I just a skeleton? Luckily, I awakened the [Undead Evolution System], which allows me to infinitely devour and evolve! While everyone else laughs at the school beauty's contract as a waste, I silently tear apart the first goblin... [Devour F-rank goblin to gain combos][Devour SSS-rank dragon to unlock Undead Catastrophe]