Two things about the unidentified girl in the background:
That barrel looks way too narrow to admit the type of ammunition she's holding. This could point to both the girl and her weapon being made up from scratch by the artist.
The joints on her striker units indicate that they are complete prosthetic replacements, making her a "Bionic Witch". Is that sort of thing canonical in the series?
Pretty sure that she's a tank-type witch (They do have those, mostly in Afrika [this place]) and that I was under the impression that the entrance to the striker unit is some sort of anomaly that your limbs disappear into... At least that's how the anime seemed to show it.
Strikers all use magical pocket dimension slots as established canon. Only a few inches of the receiver is actually clear space the rest is mechanical parts so even if most of the striker gets blown clean off it'll just slide off when the magic fails without taking off the legs.
The tank girl behind Keiko is original. No known witch has a neck guard like that. However seeing as how this appears to the artist of the actual Africa semi-canon doujin we might see her in Vol. 3.
So the girl is widdle Charlotte and striker units come with GAP HAX. I stand elucidated! Sincere thanks to my knowledgeable respondents. Many comfy cotton-clad crotches are wished for you and your progeny.
The tank appears to be a Panzer III. Not sure about the exact model, German tanks were never my specialty.
Actually it's based off of a Panzer IV derivative based off of the Panzer IV AusfH due to the use of 7.5 cm KwK 40 style "Witch combat gun" in conjunction to the "Schürzen" for additional magic shield protection for the witch...and the striker itself is called the Panzer IV "Extra Special Package".
