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.

Setelah terlibat perkelahian dengan para anggota Familia Apollo, Bell menarik perhatian pemimpin mereka, yang mengumumkan perang dengan Familia Hestia.

Hestia menolak tantangan dari Apollo, dan mundur. Namun, musuhnya tidak mau menyerahkan Bell begitu saja, dan malah melancarkan serangan keesokan harinya.

Setelah Liliruca tahu dirinya harus kembali ke Soma, Hestia memutuskan untuk menyelamatkan Lilliruca. Sementara itu, persiapan War Game melawan Apollo berlanjut.

Teman-teman Bell berdoa demi keberhasilan Bell saat ia menuju War Game. Apollo diunggulkan untuk menang, tetapi sebuah taktik mengejutkan oleh Hestia membalikkan keadaan.

Setelah berhasil menyelesaikan War Game, Familia yang anggotanya bertambah pindah ke kediaman baru. Kilas balik dari masa lalu Hestia mengacaukan rencananya.

Mikoto diam-diam keluar rumah dan bertemu dengan Chigusa, tanpa menyadari bahwa Bell dan yang lain membuntuti mereka. Mereka semua menuju ke sebuah tempat mesum.

Bell tak bisa menghilangkan Haruhime dari pikirannya, tetapi menyelamatkan Haruhime berisiko memicu War Game baru. Bahkan, lawannya ialah Familia Ishtar yang tangguh.

Upaya Bell membebaskan Haruhime membuatnya disergap oleh Ishtar. Ia dan Mikoto ditawan. Untungnya, seseorang di dalam penjara diam-diam membantu mereka.

Haruhime tetap bersama Ishtar, dan hanya tersisa sedikit waktu sebelum ritual yang menentukan nasibnya dimulai. Saat tak ada harapan lagi, tangan Bell mulai bercahaya.

Phryne meminta Haruhime menggunakan kekuatannya untuk menuntaskan persoalan dengan Bell, dan akhirnya Haruhime menurutinya. Sementara itu, Freya memasuki wilayah Ishtar.

Meski anggota kelompok Ares lebih banyak, pertarungan tidak terlalu menguntungkan bagi pihaknya. Hestia terganggu oleh hubungan Bell dengan anggota barunya, Haruhime.

Bell tiba di Edas, dan para tetua desa itu sangat ingin membantu memulihkan kesehatan Hestia. Selanjutnya, Bell mendengar legenda tentang 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.