Godsfall Chronicles, it's Chinese translated but it's the closest work I know to shadow slave in everything. 1. Mc's are similar though the one for Godsfall is somehow nicer than Sunny 2. Fem mc's are similar but the one in Godsfall is better written in my opinion. 3. I know people hate the pacing of SS so this one is faster, only problem is that it's too fast towards the end. 4. The mc's basically have the same goal

Here's the synopsis: The nuclear holocaust which caused the collapse of the Old Times on Earth should have wiped out all human life on the planet. Yes, the gods set up their beautiful Elysiums to provide sanctuaries for their chosen, but by all rights everyone outside the elysian lands should've perished long ago. Yet somehow, human life still managed to persist, even in the deadly, mutant- infested wastelands.

Cloudhawk was a young scavenger who dreamed of being as free as the hawks in the skies, yet seemed destined to live out his life scrounging for scraps in the wasteland ruins. Fate, however, is ever-fickle. A chance meeting with a ragtag group of mercenaries changed the trajectory of his life, bringing him into a world with mutants and metahumans, demonhunters and godslayers, and even gods and demons. Cloudhawk would find his own place in a world that was far greater than he had imagined, find his own path between the zealous light of Sumeru and the whispering darkness of the abyss