INTO DEEPEST MOST UNKNOWABLE DUNGEON GN VOL 1,2,3,5 (4 Manga) 
GHOST SHIP
(W/A) Kakeru
There is one place that has withstood attempts by every army to conquer it-the city-sized labyrinth known as the Deepest, Most Unknowable Dungeon. But now, after dying on Earth as a young temp worker, Jean is reborn into the world with a fascination for its most infamous dungeon. With the right training and the most carefully chosen set of lustful comrades-in-arms, he may have the chance to accomplish the impossible and become a legend in a new fantasy world!