Game-nai Saikyou no "Ura Boss" ni Tensei Shita no de, Shujinkou no Kawarini Saisoku Clear wo Mezashimasu!

Reincarnated as the Secret Boss!? I’m Going to Fail My Year!
As a hardcore gamer, one day I find myself reincarnated as the secret boss of a game I’ve been playing for years. With the goal of returning to the real world, I aim for the fastest clear possible, but nothing goes as planned!
Where’s the main character!? A mob NPC has somehow become the hero!? And why is the villainess now part of my party!?
A quirky adventure of the strongest secret boss begins—expecting nothing but chaos and unexpected twists!

(Source: BookWalker, translated)