With this seventh volume of Aneko Yusagi's increasingly good fantasy light novel series, we at last begin to not only establish a larger plot beyond “summoned heroes save the world,” but also begin to learn some of the secrets behind what's been happening with the Waves, the heroes, and all of the enchanted weaponry that seems to be floating around. Not only is it one of the tensest volumes of the series to date, but it's also one of the most important; in a sense, this is the book the previous six have been leading up to in more than a numerical sense.

Taking place over the course of only two or three days, the novel picks up directly where volume six left off, with the strange disappearances of Itsuki, Ren, and Motoyasu, the other three heroes. While the rest of the world is largely confused, Naofumi is certain that the three, who refused to learn from his discoveries about the sacred weapons, have managed to get themselves into serious trouble, if not killed. He, Filo, and Raphtalia have been searching for them and trying to kill as many of the Spirit Tortoises familiars as possible, but the attacks just seem to be getting worse and worse. It is at this point that they encounter Ost Horai, a mysterious woman claiming to be part of the Spirit Tortoise. Ost wants their help – and to help in return – with destroying the creature, stating that its mission of protecting the world has clearly gone off the rails. Naofumi realizes both that killing the Tortoise will likely destroy Ost, but also that he's in no position to refuse her offer.

Ost's assertion that something has gone dreadfully wrong with the Spirit Tortoise and that it is being controlled by some outside force is central to the ongoing plot of the series. Back in the Cal Mira Islands, Naofumi encountered Therese and L'Arc, two wielders of different magical weapons from another legend, both of whom, along with Glass, saw the four heroes from Naofumi's isekai experience as the enemy. Now it seems that yet another of these opposing heroes is behind that Spirit Tortoise crisis, and that somehow all of this is wrapped up in the truth about the Waves. Those, we learn in the short story from Glass' perspective in the back of the book, are caused when worlds intersect; the Four Holy Heroes Naofumi is a part of are meant to strictly protect the world they are summoned to while the other heroes can switch between worlds in order to wipe out the threat from Melromarc and its fellow kingdoms. Essentially, it seems, both sets of heroes are intended to protect their respective worlds in different ways, but neither are keen on the wholesale destruction of either world's population, nor in using their positions to gain power. Or rather, they aren't supposed to be – as we've seen with Itsuki's obsession with being a “hero,” personal ideals and ambitions can get in the way. But where Itsuki, Ren, and Motoyasu's immaturity caused problems relatively minor in relation to the Waves (although still awful), the rogue from the other team, Kyo, is much more destructive.

This is important because it gives Naofumi another lesson in trust. Ever since he was framed by Bitch, Naofumi has had a difficult time allowing others in, which is understandable, but it has made things more difficult for him than they've strictly needed to be. His rocky start with the other three heroes has also worked to everyone's detriment, but now with a common enemy, he's got the chance to forge a relationship with other people. Ost remarks that Naofumi has a big heart, which at first seems like a ridiculous statement, but upon reflection, proves to be correct – it is his inherent kindness (which we've seen demonstrated in his interactions and initial encounters with all three members of his team) that allowed him to be burned so badly in the first place. Naofumi does want to get along with others; but he's also not stupid and doesn't want to find himself in trouble for his trust again. The final battle against the Spirit Tortoise and Kyo forces him into a team-up that tests his unwillingness to let others in, and ultimately his interactions with Ost allow him to realize that he may be a nicer person than he thinks.

With the improvement in the story, it's a shame that One Peace Books' editing is on a bit of a downslide again, with a few cases of confused homonyms and misspellings. It isn't very much, but after the improvements in previous books, it is noticeable. Despite this, the translation remains fluid and readable, although finding a different onomatopoeia for Rishia's whine than “feh” really would be advisable, as the sound does not connote whining in English.

The ending of the volume sets things up to change completely in book eight. Ost's actions on Naofumi's behalf and Rishia's sudden awakening to her true potential – something discussed in previous books but largely unrealized until this one – have helped him to grow as a character, and his pursuit of Kyo will be very telling for those he leaves behind, namely Ren, Motoyasu, and Itsuki. Will they rise to the occasion while he's gone? Or will Naofumi remain the only true hero of the bunch? It will feel like a long wait until we get to find out.