The Deepest, Most Unknowable Dungeon is the deadliest stretch of ground in the new world into which Jean has been reincarnated. Even the top-ranked Holy Saint Slaughterer, the Queen of Darkness, and the Bow King are unable to defeat the demihuman hordes, or conquer the dungeon. But using Earth knowledge from his former life, Jean may just be able to develop the ultimate weapon--an arrow that can pierce any armor--and change the game forever!

In this Mature-rated take on the popular isekai fantasy genre, a man journeys into the darkest, squishiest depths of a goblin-filled dungeon in another world! 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!

Mere human strength is often not enough to deal with harsh and unyielding dangers--especially if you're a woman. Yearning for a way she can distinguish herself as an adventurer, Aro devotes herself to engineering and invention, perfecting a new type of arrow the world has never before seen. Meanwhile, fresh from her encounter with Rapier, the Sword Princess Katana decides the time has come to end her adventures and return home. Deeply shaken by their fateful meeting, Rapier now seeks guidance on how to deal with her new rival...

Jean and his party traverse the Untraveled Lands and make an immense discovery! Sei puts her strength to the test in a mock battle against her friends to prepare for the Holy War! In the lands of the demi-humans, the breeding pens are filling up. With no magic and no cheats, Jean has only his allies and his indomitable will--can he get strong enough, fast enough, to fight back against an entire country of monsters?!

The Deepest, Most Unknowable Dungeon is full of secrets--and dangers. Kukoro, Mexy, and Ceres come to terms with captivity as Jean continues to hone the skills of his all-female party. Meanwhile, Cross learns more about the mysterious Holy Saint Slaughterer.

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!

Surviving the Deepest, Most Unknowable Dungeon takes more than fighting skills. Jean and his all-female party are brought into the woods, stripped of everything, and start training the skills they'll need to live through the night. But will Jean be able to secure food, water, and clothing for him and the girls...or will he succumb to the temptations of other nighttime activities?

The blind Guide named Bato has her heart set on romance, and with a bit of advice from a pair of cheeky teenagers, she's doing everything she can to seduce the apple of her eye. Yet not all is well in the lands around Aegis. The redcap known as "White Mask" has long been the bane of its adventurers, and now he's been sighted once again. Ruthless, elusive, and seemingly invincible, he's claimed the lives of countless humans around humanity's walled fortress city. Jean is destined to come face-to-face with this monster of a man-hunter, and their collision will be a battle to remember!

Science graduate Kurimusubi Daisuke continues to study the complex zoology of monster girls in the fantasy world he now calls home. While bringing peace and developing technology to their villages, he sets his sights on a side quest: add one girl of each species he encounters to his personal harem!

When young adventurer Laios and his company are attacked and soundly thrashed by a dragon deep in a dungeon, the party loses all its money and provisions...and a member! They're eager to go back and save her, but there is just one problem: If they set out with no food or coin to speak of, they're sure to starve on the way! But Laios comes up with a brilliant idea: "Let's eat the monsters!" Slimes, basilisks, and even dragons...none are safe from the appetites of these dungeon-crawling gourmands!