High school student Tsukushi Kirishima is a social outcast who is looked down upon even by underclassmen. He possesses a mysterious skill called Rule Mushi, but having never found a proper use for it, he lives as an unremarkable student and explorer. One day inside a dungeon, he encounters Miru Ayatsuki, a famous streamer who is there to capture footage of an Emergency Monster, a powerful enemy that appears suddenly and draws high viewer interest. Miru finds herself overwhelmed and in mortal danger. As Tsukushi moves to help her, his dormant skill Rule Mushi awakens, allowing him to negate the monster's attacks and save her.

However, Miru had forgotten to turn off her stream. The entire rescue is broadcast live, and Tsukushi is propelled to fame overnight as a legendary explorer. The story follows the once-downtrodden Tsukushi as he navigates his sudden rise to popularity, using his unconventional skill to defeat powerful monsters while being thrust into the spotlight alongside the streamer he saved.

The setting is a modern-day Japan where dungeons have appeared, and exploring them is a common activity. The societal core of the series revolves around dungeon streaming culture, where explorers broadcast their adventures and gain fame and recognition.

The main characters are Tsukushi Kirishima, the introverted protagonist whose mysterious skill allows him to ignore established game rules, and Miru Ayatsuki, a popular and skilled dungeon streamer whose accidental broadcast changes both their lives.

Notable narrative arcs begin with the emergency monster rescue where Tsukushi's skill first manifests. Following this, he deals with the fallout of his sudden fame, including jealousy from others. He enters a duel with a rival named Kento Goyama, which is also streamed, further cementing his new reputation. The plot deepens when Goyama's mother, Yayoi, confronts Tsukushi, revealing a past connection to his father and introducing more complex antagonists. As the story progresses, Tsukushi receives a national honor award and must defend his own high school from a monster attack, facing even greater threats that push his abilities to the limit.