Zero no Shiniki

Zero no Shiniki (零の神域) is a manga series by Hana Shinohara. It was serialized in Comic Zenon.

Plot
Kanzaki Rei is an avid gamer, but one day he hit rock-bottom due to his debts. During the night while sleeping, a strange phenomenon happened and sent him inside the game he previously played. A world of life and death awaits.