Sung Jin-Woo, dubbed the weakest hunter of all mankind, grows stronger by the day with the supernatural powers he has gained. However, keeping his skills hidden becomes more difficult as dungeon-related incidents pile up around him. When Jin-Woo and a few other low-ranked hunters are the only survivors of a dungeon that turns out to be a bigger challenge than initially expected, he draws attention once again, and hunter guilds take an increased interest in him. Meanwhile, a strange hunter who has been lost for ten years returns with a dire warning about an upcoming catastrophic event. As the calamity looms closer, Jin-Woo must continue leveling up to make sure nothing stops him from reaching his ultimate goal—saving the life of his mother.

A decade ago, 450-year-old vampire Ranmaru Mori was saved from the brink of death by Rihito Tatsuno, a young and innocent boy. Ever since then, Ranmaru has been working at the Tatsuno family's bathhouse with a secret: he wants a taste of Rihito's virgin blood as soon as he turns 18. However, his plan is threatened when Rihito falls in love with a girl on his first day of high school. Jealous and scared that Rihito's pureness will be ruined, Ranmaru begins to lurk in the shadows to protect him from any harm. During his operation, the vampire must keep his real identity hidden and make sure his target's virginity remains unsullied.

Though he grew up as an orphan, Nio Chirinu finds a place to belong: being a waiter at his adoptive grandmother's restaurant. But this peace does not last long; Nio and his sister Iroha are used as bait to arrest child abductors by Toshizou Hijikata and Souji Okita—two members of an infamous ronin group called Miburo. After the ordeal, Toshizou proposes that Nio join the ranks of Miburo and protect the people of Kyoto. Frustrated by his own weakness, Nio trains to match the swordsmanship of his new comrades. Even so, he struggles to be accepted by Tarou Tanaka and Hajime Saitou, the other Miburo members of his age. Determined to befriend them, Nio must discover his own sense of justice and become strong enough to prevail against all his enemies.

Alina Clover becomes an adventurers' guild receptionist, believing that—unlike the adventurers who risk their lives every day to conquer dungeons—she will enjoy a safe and comfortable career with plenty of benefits. She hates overtime work more than anything, longing for the day when she can finally clock out on time. Sadly, that day has yet to come, as she must constantly trudge through piles upon piles of paperwork. To make matters worse, when adventurers take too long to subjugate a dungeon boss, the backlog only grows, forcing Alina into even more overtime. Whenever her patience runs thin, she dons a disguise and takes care of the boss herself, soon gaining infamy as the enigmatic "Executioner." Alina has managed to keep this secret for two years—until she finishes off a boss assigned to the high-ranking party Silver Sword. Unfortunately for her, the party's eagle-eyed leader, Jade Scrade, deduces her identity, jeopardizing the receptionist's dream of a carefree life.