What's this manga about a guy in debt who goes to a fantasy world?
The manga is Zero no Shiniki, and like you said, there's only one chapter translated so far.
Synopsis from MangaUpdates:


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.