Overall, the series seems to be a Deconstruction of the "kid superheroes in giant mechs" genre (specifically Super Sentai). 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 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 (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 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.