This whole series is from a challenge on Twitter to draw an image in less than an hour (although few people actually keep it under the time limit) being given three random characters to draw that day. (Usually, they just pick one, but Hamu Koutarou does all three.) Hamu Koutarou additionally tends to make it a theme carrying over several images, such as everyone being at the beach for several images in a row during Summer. Hamu's been doing "at the mess hall" recently.
Beyond that, I'm guessing that, because Aquilla was a character, Hamu decided to make the image about (the Japanese impression of) Italian foods, with the army of IJA Akitsu Marus scarfing it all down. Plasma's behaving like a stone-cold badass, meanwhile, because it's a running gag of Hamu's to include extreme versions of the characters.