Well, the main themes include heroism and sacrifice. The characters in the Fire Force light novel often have to put themselves in danger to protect others from the Infernals. And there's the exploration of a post - apocalyptic world where fire has a significant and often destructive role. It also delves into the moral and ethical aspects of using power, especially when it comes to the special abilities of the Fire Force members.
Shinra Kusakabe is quite interesting. His ability to use his feet as jets gives him a unique fighting style. Then there's Arthur Boyle, with his delusions of being a knight, which adds a touch of humor to the story while also making him a formidable fighter. Also, Captain Obi is interesting as he leads the 8th Company and has to deal with all the eccentric members under his command.