Otherworlder, Exploring the Dungeon, Vol. 1 (manga)

Souya, desperate for cash to pay his little sister's medical expenses, has an offer from a shady company fall into his lap-more than enough money for only a year of work...on the other side of a portal to another dimension, where he'll have to ascend to the fifty-sixth floor of a dungeon! Worse, his gig-work stint as a fantasy world adventurer gets off on the wrong foot when the transfer process malfunctions, stranding him without supplies! Will his otherworld adventure end before it even begins...?