Zero
Although it is no replacement for Seven in his affections, Zero means a lot to Katana to the point that its being damaged depresses him. Zero is symbolically the image of what Katana wishes to be, or at least what he would like others to perceive him as: something to fear. It resembles him to a slight degree, being tall, narrow and gangly, almost like a black skeleton and having glowing red eyes. Zero is the only Techode to come with an actual discharging weapon, a machine gun on its left arm. Katana has a habit of pushing Zero to its limits, as he does with himself, not recognizing damage until its so severe the Techode kicks out and breaks down in tough spots overcome with the strain.
Read more about this topic: List Of Gad Guard Characters, Main Characters, Katana