Spoiler Warning: In order to fully discuss the ending, this review will have spoilers about the final reveal.

Most people are familiar with the concept of the Bermuda Triangle. It's a mystical area stretching between Miami, San Juan, and Bermuda, and over the years a number of ships and planes have mysteriously vanished while sailing its waters. What you may not know, or remember from early volumes of Cage of Eden, is that the Pacific Ocean has its own version, the Devil's Sea or the Dragon's Triangle, with a similar mythology about missing vessels and supernatural explanations. While there have been many theories about what happens to those who go missing in these areas, one that has surfaced from time to time is the concept of a gap in reality, a place where the walls of space and time are thinner than in other places. Such spots, the stories suggest, can lead to someone taking a step through time.

This, as it turns out, is integral to the somewhat disappointing conclusion of Cage of Eden. As the series progressed before this point, the most likely theory about what had happened to the plane the protagonists were traveling on seemed to be that they had landed on an island that had held an experimental scientific community in the recent past, assuming that Akira and company were still very much in the present. This book, however, reveals that such is not the case – that instead somehow the plane has landed in a distant future where all of the passengers are assumed to have died years and years ago when their flight vanished. As an ending, it feels very out of the blue (although if you think back, there were comments about how modern the ruins seemed), and definitely as if Yamada veered towards this ending at the last minute. Had it been written around the time of Malaysia Airlines Flight 370, it could have been explained as a sensitivity issue, with the author (and his editors) not wanting to upset the grieving families of the vanished airliner, but Cage of Eden finished its serialization two years previous to that tragedy. We are therefore left to wonder what the point of the time-slip finale is.

The idea of hope certainly does still hold up – losing someone in an accident is unfortunately an everyday occurrence. But that doesn't stop it from feeling very abrupt in the way that it is presented – one moment Rion is suffering from a strange slime-mold biohazard, and the next Akira is figuring out that they're in the future. Virtually no time is devoted to the question of why such a biohazard would exist, much less be unleashed on the facility, and the recovery takes little to no time, which is not normal for a series that devoted pages and pages to the effects of head injuries and mental stress on its characters. Simply put, it feels like a last-minute cop out, which is not what you want to give your readers after twenty-one volumes of tension.

The title does imply that Yamada had some idea about building a “Garden of Eden” initially, and that that paradise would become a trap to the characters. He makes that a bit too obvious with the collection of Edenic artwork that the group discovers in the third tower, although the scene with them finding their pictures and tombstone is very effective. (It may be worth considering that the TV show Lost did conclude during Cage of Eden's serialization, which may have made Yamada decide to switch directions.) The idea of a supposedly Perfect World that has in fact become a deadly cage is an interesting one, and if Yamada doesn't wrap it up nicely, he does continue to play with it as a theme in this volume, which is one of the stronger aspects. His art remains strong as well, with the structures and people aging believably and a general toning-down of the fanservice in the tenser scenes, where it would have distracted from the action and information being presented.

Cage of Eden's finale is definitely a disappointment. While Yamada does manage to make it work to a degree, it still feels rushed and half-assed, as if it were thrown together at the last minute due to an abrupt change of plan. One of the key rules in creative writing, as phrased by author Nancy Lamb, is that authors must always keep their promises to their readers. Cage of Eden, despite giving us the promised solution to its mystery, does not do so adequately, making the previous twenty books in the series feel a little like time wasted. It isn't a disastrous ending (it does stick with accepted Devil's/Dragon's Triangle mythology), but it also isn't as satisfying as it could have been with all Akira and his friends have fought for. Yamada fulfils his promise in the barest of terms. After twenty-one volumes, that really isn't enough.