The protagonist, a young man aiming for a successful high school debut, decides to become an "Explorer" to gain recognition. Explorers are individuals who awaken special abilities allowing them to enter "Dungeons," mysterious labyrinths that appeared globally, and fight the monsters within. Dungeons are also valuable sources of resources, treasure, and sustenance. To become an Explorer, one must register with the Explorer's Guild and pass an aptitude test.
Arriving at the clean, public-institution-like Explorer's Guild, the protagonist, disguised with a hat and mask to maintain his anonymity, waits for his turn. He is struck by the beauty of the receptionist, Kurosaki Rei, a young woman with striking features. After filling out an application, Rei uses her "Appraisal" skill to assess his aptitude. To her surprise, the protagonist's status screen shows no level, ability points, or skills, which is highly unusual. Despite this anomaly, he is deemed to have aptitude.
Overjoyed at first, the protagonist's excitement quickly turns to despair upon learning about his peculiar status. Rei, however, reassures him that his stats will likely appear once he enters a Dungeon and defeats monsters. This offers a glimmer of hope, and he proceeds with the Explorer registration, receiving an Explorer Card. He learns he can officially enter Dungeons once he turns sixteen, which is soon, allowing him to potentially catch up to his peers.
Returning home, the protagonist shares his unusual situation with his younger sister, Nanami, who finds it hilariously ironic. Despite her amusement, Nanami expresses concern for his safety. The protagonist reassures her, emphasizing that he will enter the weakest F-rank Dungeon to awaken his stats. He spends time researching his condition online but finds no similar cases. Determined, he decides to prepare for his first Dungeon dive.
The next day, April 3rd, after a small birthday celebration with Nanami, the protagonist heads to an F-rank Dungeon. He dons basic protective gear, as high-level equipment is prohibitively expensive for beginners. Nanami expresses her desire to explore Dungeons too, but he explains she must wait until she's sixteen and has confirmed aptitude. At the Dungeon entrance, a guard checks his Explorer Card and notes his unusual lack of visible weaponry, advising him to get proper gear for higher-ranked Dungeons. After passing through the authentication gate, the protagonist steps into the Dungeon, ready to face his first challenge and awaken his dormant abilities.
