Z’s Longest Day (Ｚの一番長い日, Z no Ichiban Nagai hi) is the 5th volume in the series.
- Chapter 11: Don't Forget to Don't Forget Me
- Chapter 12: Zapp's Longest Day, Part 1
- Chapter 13: Zapp's Longest Day, Part 2
An escaped Blood Breed brings Libra operative Zap Renfro’s former master to New Jerusalem, and Zap must once again prove his skills to avoid being dragged back to the harsh training grounds of his school. And though Zap is a formidable fighter, he’ll need the assistance of the other Libra agents and his own young apprentice to imprison the Blood Breed before it wreaks untold havoc upon our world!