I really enjoy this specific piece. I love how you tried to mimic the manga style, but with your own style added in. Some things I would suggest working on although, is some of the features. I find that the collar of Keneki's shirt is a bit outstanding, and the size of it makes it seem like it's more of the key focus rather than his hunger.
Another thing I notice is the teeth print of his mask are a little too realistic for the rest of the design. Everything else is very similar to manga styles, then it seems the design on his mask is overly realistic to fit in with the rest of the image.
Other than those two points, this is really well done! I love how you depicted his emotions in this, as well as the manga-like style. Another key thing I like about this is how you did the blood effect. It's a bit much in some points, but it really pulls this whole image together.
Keep up the amazing work!