With its third novel The Devil is a Part-Timer! continues the story beyond its anime adaptation, in the process making it clearer that there is a much bigger story involved than what the anime version hinted at. Minor revelations throughout the story, coupled with a bombshell dropped in the book's final line, show that even individuals as prominent as the Hero and Devil King did not fully comprehend all of the mysteries operating behind them. And one of the biggest of those has to do with the nature of Emi's holy sword. After all, there is a particular meaning to it bearing the odd name of Better Half.

But let's not get ahead of ourselves here. The bulk of the story is about the entire cast introduced so far having to deal with Alas Ramus, and that does provide all sorts of interesting complications since the only one of them with much experience dealing with little kids is Chiho; for instance, the demons of the Devil's Castle do not even have enough experience to know that a diaper might need to be changed, much less how to do it. Considerable humor comes from the way the precocious toddler can flummox individuals who wouldn't flinch in the face of lethal combat, although the ornery staircase to the apartment building and the pathetic living conditions of the devils also get their regular turns. The contradiction inherent in Mao seeming to take seriously being a parent can also be amusing, as does he and Chiho having to come up with an explanation about Alas Ramus to their boss. And of course Urushihara continues to get ragged on at every opportunity and continues to deserve it.

What the whole business does not lead to is a stronger leaning towards romance for Emi and Mao; if that is ever to be in the cards, it will not be for some time yet. Mao and Emi still quite clearly hate each other, and their efforts to work together for the sake of Alas Ramus (perhaps not coincidentally) smack more of a divorced couple who just barely still tolerate each other for their child's sake. Their efforts do, however, bring out considerably more background about Mao's past before he became the Devil King and his possible motivations for taking over Enta Isla. That background offers some peculiar twists which will doubtless presage developments in later novels and gives Emi pause to consider how almost humanlike Mao's past is. Their efforts also unwittingly bring Emi's coworker Rika back into the picture, where her attraction to Ashiya gets considerably reinforced.

As with the previous two novels, the writing is heavy with snappy dialog exchanges and precise detail; author Satoshi Wagahara comments in the Afterword that he did quite a bit of research about basic child-rearing for this novel, and the effort shows. He also follows a long-standing anime/manga/light novel tradition by delving deeply into the Sephiroth, which is only slightly altered in its adaptation from original Kabbalah sources to serve as the cosmological template for the reality that Enta Isla exists in. The way Alas Ramus fits into that is rather clever, as are the reasons why she is inclined to call Mao “Daddy” and Emi “Mommy.” The resolution of her situation at the end also takes an unexpected – though not illogical – twist which will have big continuing complications for both Emi and Mao. More questionable is the personality of a second archangel who eventually appears on the scene late in the story, although his idiosyncratic speech style could also be a product of curious translation choices. Still, he does at least distinctively stand out when talking, which is good because the dialog has an annoying tendency to skimp on labeling the speaker, to the point of obfuscating who is saying what in some cases.

Yen Press 's release of the third volume used a translated version of the original Japanese cover. Instead of multiple glossy art pages at the beginning (as the previous two volumes had) it has a single glossy trifold depicting the female characters on one side and the male characters on the other. The handful of black-and-white illustrations throughout are well-done, though sadly none of them depict the new archangel. 251 pages of actual story are followed by four pages of Afterword by both Wagahara and illustrator 029 (Oniku), a résumé page for Alas Ramus, and a diagram depicting Urushihara's closet hideaway.