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.

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.

Unlike his twin brother, Yukio, Rin Okumura never wished to know about their parents and the circumstances surrounding his own birth. Yet the master of time, Mephisto Pheles, gives Rin a key that transports him 40 years into the past when his late mother, Yuri Frederick Egin, was merely a child. With Mephisto's guidance, Rin leaps through the years of Yuri's childhood and her adolescence as an exorcist-in-training. Early on, Yuri meets Shirou Fujimoto, Rin and Yukio's adoptive father. As Rin follows Yuri and Shirou's lives, he witnesses firsthand the initial appearances of Satan, his true father, and the horrors unfolding at the True Cross Order's special Section 13. Yuri's unique connection to Satan eventually leads Rin to the truth behind the most horrific event in exorcist history and the day he and Yukio were born—the Blue Night.

The second season of Watashi no Shiawase na Kekkon.