|Romaji||En En no Shōbōtai 04|
|Pages|| 192 (JP)|
|Japan||August 17, 2016|
|North America||June 13, 2017|
|United Kingdom||June 13, 2017|
|List of Volumes|
Shinra has discovered that someone is using a bug to turn people into Infernals. He’s narrowed the suspects down to two, and now he must figure out which one is the real culprit. Can he find out who is friend and who is foe without first getting caught himself?
- Chapter 26: Infernal Bugs
- Chapter 27: Unpardonable Evil
- Chapter 28: Shinra vs. Rekka
- Chapter 29: Fists or Feet
- Chapter 30: The Man at his Back
- Chapter 31: Scorching Malice
- Chapter 32: A New Menace
- Chapter 33: Heroes Assemble
- Chapter 34: The Boy Knight
- In its first week of sales, Volume 4 reached the 21st place on the official Oricon manga rankings chart, and has sold an estimated amount of 49,737 copies.
- The Japanese volume also included an official character profile for Maki Oze revealing personal information about her such as her height, weight and favourite food.
- In the Afterword Manga: Atsushiya section of this volume, the author Atsushi Ōkubo clears some concepts that might have confused some readers, explaining his enthusiasm for the official westernized name for his manga series (Fire Force), and changing the "Fire Soldier" on the brigade members' helmets to "Fire Force" due to it not making sense when looking at it from a team perspective. The name "Fire Force" was suggested as well as "Fire Squad" - with the former being chosen due to "squad" meaning a small-scale military team, in comparison to the large force that is the Special Fire Force.