The battle against the Insectors to save the Inner World rages on, as Hunter Steele and the Spider Riders defend Arachna. With the help of his friends—Igneous, an intelligent young royal officer of Arachna's military; Magma, a foolhardy warrior; and Corona, a kind-hearted girl—crisis has been averted—but not for long. News of the Kingdom of Nuuma being attacked by the Insectors is soon brought to the attention of the Spider Riders, who are reluctant to leave Arachna undefended. But past favors need to be repaid, so they decide to travel across the Inner Ocean to protect the Kingdom of Nuuma. Entrusted with finding four of the Oracle's keys locked away by the leader of the Insectors, Hunter and his friends strive to bring about peace once and for all. Spider Riders: Yomigaeru Taiyou is the epic conclusion to the Spider Riders series. Will the four Oracle Keys find their way to Hunter and the Spider Riders, or will Mantid and the Insectors finally have their wish granted, conquering the Inner World for themselves?

Corrupt politicians, frenzied nationalists, and other warmongering forces constantly jeopardize the thin veneer of peace between neighboring countries Ostania and Westalis. In spite of their plots, renowned spy and master of disguise Twilight fulfills dangerous missions one after another in the hope that no child will have to experience the horrors of war. In the bustling Ostanian city of Berlint, Twilight dons the alias of Loid Forger, an esteemed psychiatrist. However, his true intention is to gather intelligence on prominent politician Donovan Desmond, who only appears rarely in public at his sons' school: the prestigious Eden Academy. Enlisting the help of unmarried city hall clerk Yor Briar to act as his wife and adopting the curious six-year-old orphan Anya as his daughter, Loid enacts his master plan. He will enroll Anya in Eden Academy, where Loid hopes she will excel and give him the opportunity to meet Donovan without arousing suspicion. Unfortunately for Loid, even a man of his talents has trouble playing the figure of a loving father and husband. And just like Loid is hiding his true identity, Yor—who is an underground assassin known as Thorn Princess—and Anya—an esper who can read people's minds—have no plans to disclose their own secrets either. Although this picture-perfect family is founded on deception, the Forgers gradually come to understand that the love they share for one another trumps all else.

Loid Forger, an elite spy, is warned by his handler that he may potentially be reassigned from his ongoing mission, Operation Strix. To maintain his position, he must make significant progress toward the operation's objectives, which involves having his adoptive daughter Anya earn sufficient Stella Stars to become an Imperial Scholar at Eden Academy. After learning of a cooking contest that awards the winning student with a Stella Star, Loid researches the judge's preferred dessert to help increase Anya's odds. However, perfectly recreating the judge's favorite meremere requires more than just following a recipe. Thus, the Forgers embark on a vacation to the Frigis region to try an authentic meremere. Not all goes smoothly on the trip, as the Forger family ends up entwined in a sinister plot to reignite war between the countries of Ostania and Westalis.

With Anya Forger successfully enrolled at the renowned Eden Academy, Operation Strix advances to its second phase. To investigate Ostanian politician Donovan Desmond, Anya must either befriend his son Damian or collect eight Stella Stars to become an Imperial Scholar. Fortunately, Anya has already acquired her first star. In celebration, her adoptive father, Loid, decides to fulfill her wish to adopt a dog. During their canine search, Loid receives new orders from his superiors, who have found that a band of Berlint University students is plotting to assassinate Westalis' Minister Brantz using bombs worn by trained dogs. While Loid tries to stop their plans, Anya stumbles upon the terrorists' base of operations. There, she befriends a kindhearted, clairvoyant dog who the family later names Bond. Although the Forgers continue to lead their individual lives in secrecy, the family—with a new fluffy addition—remains united through all of the unusual obstacles thrown their way.