Sentou Jousai Masurawo
"Kawamura Hideo, a typical ordinary guy with no job, came to Tokyo searching for jobs. He sent a total of 34 job applications only to fail at the first hurdle (the companies didn't even ask him for an interview). Feeling rejected he became a hardcore hikikomori and shut the world around him, his parents also won't send him money since then. When he was starving to death without any money, lopsing hope and deciding to die, he found a computer on the street (containing Will.CO21 virus) and took it home.
He found a way to participate in a martial arts tournament "Holy Devil Cup" from that computer. Where the winner could get the power to rule the world, martial artists, soldiers, vampires, Majin - all 3024 participants gather there. Now what Hideo would do to win this mad tournament... "
I really enjoyed the manga, didn't realize it was a light novel too. Would be interested in reading it.
Those were my thoughts exactly. I read a couple reviews on the LN years ago, and they were quite positive. I'd consider this a hidden gem. Fingers crossed!