After identities were revealed from the previous volume, more secrets are unraveled as this volume ponders the origin of human evolution and the Guyver units, and the action picks up from where it left off in the previous episode.

Starting with the second part of the episode "The Tragic Enzyme," Sho returns to Relic's Point to rescue his father with the help of Agito, but the rescue, all but routine, turns tragic, as Sho must face against his father who was optimized into a Zoanoid called Enzyme. Unable to fight against his father, the creature manages to take advantage of the situation until the Guyver unit decides to turn on its emergency self-defense mode to preserve itself. At the same time, Chronos continues to hit hard, as they send two of their powerful Zoanoids to eliminate Sho's friend at their current hideout. Having no chance of escape, Murakami is forced to show his true ability and form as a prototype Zoalord to fend off the attack.

Now on the run and Sho barely remembering anything that happened in his previous battle, his armor suddenly disengages when he is about to engage Zoanoid Enzymes, and he is unable to transform back as Guyver Unit 1 – a psychological effect from his encounter with his father.  Once again, Murakami must transform to save everyone from the attack, which forces Guyot to join the fray on their next attack with his true form and strength as a Zoalord.

Separated during Guyot's attack, and still unable to transform, Sho decides that he will protect Mizuki and promises to set everything right.

While the series continues to pile the high-intensity action, this volume also manages to dwell on the origin of "Creators," the alien life forms that single-handedly created and manipulated evolution on Earth, and that humans are the basis of biological warfare. As for the Guyver units, although considered standard equipment for the "Creators," it became a threat to them as whoever is equipped with the unit has his own free will without any mind link to the "Creators." To make matters worse, Zoalords equipped with the Guyver unit will become more powerful than the "Creators" themselves, a knowledge that Guyot is well aware of, and the reason why he is persistent in retrieving the Guyver unit.

EXTRAS:
The extras once again sport four manga / anime comparisons, as it shows how much the series follows its origin. A commentary of Episode 13 with Lowell Bartholomee (Tetsuro) and ADR Director Charles Campbell, as they talk briefly talk about the previous Guyver versions, how the current version keeps its original story, and teases the viewer on what happened at the end of Episode 15. The DVD also comes with The Bioboosted Armor Guyver Master File 2, which features character profiles, Japanese staff interview, and episode synopsis of Volume 4.

IN SUMMARY:
More action, more mayhem, and more fun. The series continues to drive its riveting story well into your mind, making you want more. It is an tribute to what a series can do when its story is based on the original material.