Transmigration Upgrade Specialist

After transmigration, Zhang Wu Ji is reincarnated into a youngster body with the same name.

Their differences?

Before reincarnated, he was a poor librarian that have to sleep in the library because he can't afford to rent a room. After reincarnated, he was a poor bastard that was despised by his two elder brothers because he was born with a worthless Martial Constitution.

But as a Transmigrator, he possessed a special System, [Upgrade] that allows him to strengthen anything in this world. How would he fare when he will need to earn, create, upgrade, and upgrade even more to reach the peak of the world?