The Labyrinth city of Orario has a massive dungeon at its heart, filled with terrifying beasts. A new adventurer, Bell Crannel, challenges this perilous labyrinth, but not in hopes of finding treasure, but in hopes of picking up a girl.

Bell Crannel's power grows rapidly thanks to his ability, Realis Phrase. As long as he's in love with a girl, it will continue to make him stronger. His goddess, Hestia, is jealous that the girl he's in love with isn't her, but still wants to support him. She goes to another goddess and asks her to make him a powerful sword.

"I don't want to lose any more of my family." Bell and Hestia are attacked by an escaped monster during Monster Philia. Bell fights to save the only family he has left, but is overwhlemed by the monster.

"Excuse me, are you looking for a supporter?" After his rapid growth, Bell reaches the 7th floor of the dungeon. He gets new equipment and is ready to go when a girl named Lilika approaches him. She is a supporter, and her job is to aide adventurers in the dungeon.

With Lili's help, Bell is progressing further into the dungeon than ever. Since he can focus on the fights, he can make more money. But Lili has a secret: she despises adventurers, and is waiting for a chance to trick Bell.

Lili leads Bell deep into a dungeon and abandons him. He's alone and surrounded by larger monsters than he's ever faced. She runs off with his knife and makes for the exit, but her guild mates are waiting for her.

At Bell's urging, Hestia reluctantly lets Lili into the party. Bell, worried about his weakness as he continues to go deeper into the dungeons, accepts an offer of help from Aiz Wallenstein, the girl he loves.

For an adventurer to level up, and truly get stronger, he has to go on an adventure. Bell travels down to the lowest of the upper floors of the dungeon, where he encounters a minotaur with a giant sword. Lili is badly injured, and Bell is unable to leave her behind. Aiz arrives again to save him, but he waves her off...

Bell defeats the minotaur and becomes the fastest adventurer to level up in history. After his success, Bell is given the nickname "Little Rookie." As he sets his sights on the middle floors of the dungeon, Ryuu tells him that if he wants to succeed, he's going to need a bigger party.

The party is exploring on the middle floors when another group leads a huge train of monsters to them. They're overwhelmed and caught in a cave-in. Cut off from the upper floors, with limited supplies and little strength left, they are forced to make a desperate attempt to reach the safe zone even deeper in the dungeon.

After a great struggle, Bell and his party finally reach the 18th floor. Aiz Wallenstein and the Loki Familia are already there, returning from their expedition to the lowest levels of the dungeon. With the danger passed, they enjoy a short break before they head back up to the town.

A massive floor boss has crashed down from the upper floors and begun tearing apart the adventurers. Aiz has left for the surface, and it's up to Bell and his friends to defeat the monster. With their escape route cut off, it's do or die if they ever want to see the light of the sun again.

A massive floor boss falls from above and traps the adventurers. The only way out is up, and to get back home Bell will have to defeat it without Aiz's help.

Selepas terlibat dalam pergaduhan dengan ahli Familia Apollo, Bell menarik perhatian pemimpinnya, yang mengisytiharkan perang terhadap Familia Hestia.

Hestia menolak cabaran Apollo dan berlalu pergi. Namun, penentangnya tidak mahu melepaskan Bell begitu sahaja lalu membuat serangan keesokan hari.

Selepas Liliruca menyedari dia mesti pulang ke Soma, Hestia membuat keputusan menyelamatkannya. Sementara itu, persediaan Permainan Perang menentang Apollo diteruskan.

Rakan Bell mengucapkan selamat kepadanya ketika dia menuju Permainan Perang. Apollo dijangka akan menang tetapi taktik mengejutkan daripada Hestia membalikkan situasi.

Setelah berjaya melepasi Permainan Perang, Familia yang kian berkembang berpindah ke kediaman baharu. Sesuatu dari masa lalu Hestia merosakkan rancangannya.

Mikoto menyelinap keluar untuk bertemu Chigusa, tanpa menyedari Bell dan yang lain mengekori mereka. Kesemua mereka pergi ke suatu tempat yang penuh berahi.

Bell tidak dapat melupakan Haruhime si perempuan musang tetapi menyelamatkannya akan merisikokan Permainan Perang lain, kali ini dengan Familia Ishtar yang lebih kuat.

Perjalanan Bell untuk melepaskan Haruhime menyebabkan dia diserang Ishtar lalu dia dan Mikoto dipenjarakan. Mujurlah seseorang di dalam penjara membantunya secara senyap.

Haruhime kekal bersama Ishtar dan tinggal sedikit masa sehingga upacara yang akan menentukan nasibnya. Ketika semuanya tampak tiada harapan, tangan Bell mula bercahaya.

Phryne memerintahkan Haruhime menggunakan kuasanya untuk memuktamadkan urusan dengan Bell, dan dia menurut. Sementara itu, Freya meneruskan kembara ke wilayah Ishtar.

Meskipun bilangan Ares begitu ramai, perlawanan tidak begitu baik baginya. Hestia bimbangkan hubungan antara Bell dengan ahli terbaharu mereka, Haruhime.

Bell berakhir di Edas, suatu tempat yang orang tua di kampung itu bersedia merawat Hestia agar kembali pulih. Kemudian, dia terdengar tentang legenda Naga Hitam.

Monsters are evil abominations driven by murderous instinct. But if that were true, why is this one a scared little girl who doesn’t understand why she’s being hunted?

Who knows what could happen if word of Wiene’s existence spread. The Hestia Familia needs answers and soon, but what they discover in the dungeon only raises more questions...

The Guild knows about Wiene. But instead of demanding answers, it assigns the Hestia Familia a mission they cannot refuse. Something awaits them in the dungeon’s darkness.

There are others like Wiene, and they call themselves Xenos. Uranus asks much from the Hestia Familia, but if anyone can bridge the gap between species, it’s them.

It was supposed to be the dawning of a new era. But selfish, evil men only care about what they can take for themselves, leaving others to face the consequences.

Bell shouldn’t get involved. But the young adventurer has already decided otherwise. Little does he know that he’ll help Fels discover a secret even Uranus doesn’t know.

Never underestimate the measures a fanatic will take to prove his worldview correct.

The Loki Familia are battle-hardened veterans used to fighting monsters. But this opponent is different...

Although Ikelos has been successfully scapegoated, public opinion turns on Bell. Helping the Xenos will now prove impossible — but Hermes’ intel might just change the tide.

The surface is no longer safe for the Xenos. Now, the Hestia Familia must smuggle them back into the Dungeon. There’s just one problem: The Loki Familia stand in the way.

Bell WILL stay true to his ideals. Even if that means making an enemy of the woman he loves.

As Hermes finally reveals his true intentions, Bell battles the most powerful opponent he's ever faced.