Game-nai Saikyou no "Ura Boss" ni Tensei Shita node, Shujinkou no Kawari ni Saisoku Clear o Mezashimasu!

"Reincarnated as the Hidden Boss!? I'm gonna end up repeating a year!" One day, I, a degenerate gamer, found myself reincarnated as the hidden boss of the game I was grinding. In order to return to the real world, I'm aiming for the fastest clear.. but nothing goes as planned!? Where's the protagonist of the game?! A random NPC became the hero?! And why did the villainess join my party?! The hilarious adventure of the strongest hidden boss begins now!!