This crummy minimalist art and that short hair remind me of manga-Phos.
I wouldn't call the manga art of Houseki No Kuni crummy personally, it's not ultra detailed sure but I like the style plus the visuals in general look pretty nice in my opinion. It has far better art than this one-shot, at the very least in terms of execution, but I can see how the tomboy in this had some resemblance to Phos.
Edit: Also as other people here have have said I'm mostly reminded of Levi from Attack On Titan.
last edited at Nov 14, 2018 5:09AM