Remember how great AiON's first volume was, with its multiple themes and plotlines woven into a single gripping narrative? Remember how it was about school bullying, and strained family ties, and mysterious creatures with mind control powers—and how all of it was ultimately connected to the odd but growing friendship between Tatsuya and Seine?

Alas, how quickly that greatness disappears.

The promise of complexity and excitement in Volume 1 ends up being broken in Volume 2, which cuts a much more linear (and therefore much more boring) path. Gone are the intriguing, character-building side plots, and even the central premise of the series is diluted to a mere shadow of itself. Seine's next mermaid-vanquishing mission doesn't really get started until about halfway through this volume, which of course means that the installment ends with the deed only halfway done. (The dramatic cliffhanger finish is hardly a consolation, since it's the kind of over-the-top "irreversible" plot point that will inevitably be reversed.) Even the title character only makes a brief cameo, slithering through a single scene as an act of foreshadowing but not actually engaging in any spirit-battling action. Maybe this is just crazy talk, but if a series is called AiON, the entity known as AiON ought to be more heavily involved in it.

So what actually does happen in this volume, if not multi-layered supernatural intrigue? The answer is lots of side-character waffling and wandering, which in some cases does matter—certainly Nagisa's feelings for Tatsuya are essential to her succumbing to evil—but a lot of the material still drifts too far away from the main plot. Too much time is spent on Tatsuya hanging out with his classmates: almost a third of the book, which is too much slice-of-life school comedy for what is supposed to be a fantasy-action series. Meanwhile, the twin demon sisters who butt in on Tatsuya and Seine's life end up being more of a distraction than a contribution, engaging in pointless slapstick antics and only being useful during flashbacks about Seine's past. The only character interaction that's truly effective is when Seine uses psychological gamesmanship to bring out the spirit lurking in Nagisa—and that doesn't start in earnest until after around Page 100.

All of this might be forgivable if there were at least some attractive visuals to look at, but readers will find no such luck here. Yuna Kagesaki is one of those manga-ka who isn't blessed with tremedous artistic gifts, and so has to use her rich storytelling skills to sell a series. But what happens when the storytelling hits a wall? The artistic shortcomings become that much more obvious, from the failed attempts at perspective (a strangely skewed bed floats in middle of the school sickroom) to the middling character designs (try to recall the faces of any of Tatsuya's second-tier classmates ... not so easy, is it?). At least there's clear, straightforward paneling to keep the story moving, but when the story is mostly dull supporting-character interaction, a well-planned layout doesn't hold much value. The numerous scenes of day-to-day life and grade-school flashbacks also make for uninteresting backgrounds; even the coastal views from around Tatsuya's hometown lack the richness needed to evoke a genuine seaside feel.

Where the storytelling and visuals fall short, the dialogue tries to compensate and almost gets away with it—some of the verbal exchanges, especially the more heated ones, are loaded with an energy that is missing from the overall story. Credit some of that to the translation, which isn't afraid to show off a bit of attitude in the way the characters talk (and thankfully without going overboard). Whether it's just a quip between friends or a declaration of outright hatred, the script is one of the few things in this volume that is at least somewhat entertaining. Translation is spottier on the sound effects, however, with much of it left in raw Japanese and only the occasional "thunk" or "smack" being added into the art at the discretion of the translator. For a series that uses sound effects fairly frequently, this kind of negligence is a big mistake.

Which is worse, then: a series that was mediocre to start with, or one that lapses into mediocrity after a promising start? The second volume of AiON may help to answer that question, as it sheds much of the complexity that made the first volume so interesting and goes for a pedestrian, slice-of-school-life approach that is saved only by lively conversation and occasional flashbacks. By the time the story starts to get back some of its suspense and supernatural vibe, this volume is already halfway over, and it doesn't help that supporting characters keep butting in with their time-wasting antics. What really feels terrible about all this is not slogging through the poorly crafted pages, but knowing that Yuna Kagesaki can do a lot better.