Overall, the series seems to be a Deconstruction of the "kid superheroes in giant mechs" genre (specifically SuperSentai). The series, and many individual chapters, starts out with traditional superhero situations which quickly break down in a realistic fashion. Blitz's dad supports her vigilante activity at first because he agrees that the police force is unequipped to deal with criminals in mechs, but he immediately regrets it and constantly worries that his daughter is going to get killed by the psychos she attracts. The series takes pains to portray criminals as being either psychopathic nutcases or cold-blooded and intelligent, which stands in stark contrast to the usual incompetent villains of most series involving mechs.
One thing of particular interest in this comic is the use of the music theme: the chapters are called "track" and named after various songs. There doesn't seem to be much use of music in the actual comic, so the reason for this isn't readily apparent. However after Steffi explains how she lost her leg during [[http://www.kiwiblitz.com/comic/track-1013 Track 10]], the reason for the theme starts to be explained better. While bleeding out on the sidewalk after taking the bullet for her father, we see ([[http://www.kiwiblitz.com/comic/track-10-bite here]]) that Steffi is afraid of death, and that silence symbolizes death. This also links back to the earlier comic during Steffie's first fight with Gear, when she is momentarily stunned, she hallucinates [[http://www.kiwiblitz.com/comic/track-0611/ laying on the sidewalk next to her younger self]], and the speech, presumably in her own voice says that "even when you're not conscious... it's still there at the back of your mind. Reminding you that you're still alive."
So from this, it seems that Steffi's fears, especially death, are represented by silence, and this explains both the music theme of the comic, and the fact that Steffi is almost never seen without her headphones on, no matter what she's doing. We can expect that once Steffi goes through some more character development, she will remove the headphones to symbolically show that she has grown enough to face her fears without the music. This will probably involve her coming to better appreciate and stand on the support that her friends, especially Ben, give her.
Gear is shown since her first appearance to have blatant disregard for human life. Her murdering "style", as it were, is a combo of [[https://en.wikipedia.org/wiki/Spree_killer spree killing]], [[https://en.wikipedia.org/wiki/Thrill_killing thrill killing]], and [[https://en.wikipedia.org/wiki/Depraved-heart_murder depraved-heart killing]]. But aside from unspecified mental illnesses, where does this disregard come from? Most serial killers become killers due to ingrained mental problems and horrendously awful childhoods. Does having your family get bombed away and your left side violently lost in the same explosion count as horrendously awful? Undoubtedly. Though, the bombing was a single event, while serial killers tend to have prolonged awful childhoods chock-full of abuse. We don't know if Gear experienced such, but back to the bombing...
Explosions on their own are traumatic - but equally traumatic is the waiting period before rescue. Prisoned under tons of debris, severely injured, too weak to scream, and listening to the whispers for help only others in the same situation can hear: horrific. Survivors could wait days before rescue. Many would watch their fellow sufferers die around them, and sometimes lifting equipment cut limbs as well as rubble. Some even had dead people on top of them - in fact, it's VERY likely Gear had the body of one of her dead parents on top of her. It's also likely she got flung on a wall and had most of her bones crushed (not mutually inclusive). And you know how eyes are most frequently lost in explosions? Fragments of debris flung outwards by the blast. Usually major brain damage results from this, too, but Gear seems to have gotten lucky. The kicker? All of the above are amplified in a confined area, like a mine or subway station.
Furthermore, she was about 6-7 at the time, where children are still learning moral values and connecting them to the world at large. And what would a child learn from this? 1) Everyone you love can be taken from you in an instant, and 2) creatures suffer and die uselessly, without reason or weight. That's some heavy shit to lay on a six-year-old!