I'm The Main Character in An Extra Novel!?

Imagine you a reader, reincarnated into a novel world. Not destined to be the Chosen One. Not as the dazzling, charismatic protagonist destined to save the entire world. I thought I was just an insignificant extra but turns out I am that protagonist. My name is Lumen Shakov, and I am The Hero. I clawed my way up from utter filth, bled for the justice of those victims, a person who fought alongside The Phantom Guild. They called me the Ghost Detective. The man who cracked the toughest of cases behind the scenes, completely surrounded in ghastly mystery. But what did all that matter? My parents? Victims of the war. My friends? Tortured and broken beyond repair. The Phantom Guild? Massacred and flattened to the ground. And then I learned the stark reality of this world. It was all a story. My suffering. My struggles. My entire life! —Nothing? But the whim of a bastard sitting behind his screen. "You’re telling me… my entire life isn't even real?" My hands trembled vigorously, my fingers twitching as if I was a broken puppet. My breath hitched, sharp and heavy, scraping my throat like a knife. "Why!?" "Why me!? Why was I your protagonist... why?" I clawed at my scalp, nails clutching my strands of golden hair, but the pain was negligible—just like the rest of this horrid world. "How? How...?" And then— [Congratulations, you have unlocked Forbidden Knowledge.] [Gift Acquired: Keeper of the Forbidden Knowledge.] Now, I see the very threads of fate. The quick slow turning of a page resounding in my head. "I won't be shackled by your dam words... You bastard author!"