This Detective Only Knows How to Launch Sneak Attacks

Three days ago, someone claimed to have witnessed something wondrous and terrifying, unlike anything he'd ever seen, in a forbidden place on the mountain. Even stranger, everyone who went to the forbidden place mysteriously disappeared. The town at the foot of the mountain suddenly fell silent and lifeless, shrouded in mist. The case quickly became incredibly difficult to crack. The survivors decided to turn it into a bounty, calling on assassins and mercenaries who would do anything for money to solve it. A drunken man yanked down the notice. He looked like an assassin from a bygone age. "Boss, how much is this job worth? I'll take it."