7002 Book(s) Related to PROTECT THE PRINCESS: THE HIDDEN WARRIOR

Kael Drant did not lose everything because he was weak. He lost everything because he was right.
Framed for a crime he did not commit, sentenced to fifteen years in Vault 9 a monster containment prison built inside an active dungeon rift Kael has no combat skills, no allies, and no power.
What he has is a skill nobody values and everyone overlooks. Analytical Eye. The ability to see beneath the surface of anything he studies. And a System mechanic nobody has ever discovered: the deeper he understands something, the stronger he becomes against it.
The hunters outside have raw power. Kael has something more dangerous.
He has time to think.
And he just found his dead father's handwriting on the wall of his cell

After I retired, I was willing to do the dirtiest work at a small auto repair shop—just to give my sick daughter an ordinary childhood.
I endured my mother’s insults, my eldest brother’s wage cuts, my younger brother’s extortion.
But they actually joined forces to steal my daughter’s life-saving money for gambling, then sold me into an illegal mine to pay off their debts.
When the iron chain locked around my wrist, when my daughter cried in despair, the killing intent that had slept in my blood for three years finally woke up completely.
They had no idea I was once the iron-blooded God of War—commander of a million troops, the name that made enemy nations tremble.