Hi there. Just be patient with replies, sometimes it can take a few days to get some good critique in this forum.
I like your drawings quite a lot, they're very cute and have a lot of potential. Especially how you are drawing using a very generic form (anime) but you don't conform to the general constrictions - for instance, your proportions are realistic, as opposed to the general giant-headedness of the anime style.
The main tip I would have is to work on your anatomy. For instance, your face seems a little off, in that the mouth is too far to the right. Also, the hair seems to sit flat on the head like a helmet, possibly because the head is very round at the chin and doesn't seem to extend upwards as far as it should.
Your arms are fantastic! I am really impressed here, as I find this is one of the hardest elements of drawing anatomy. However, despite the waist being pretty great on the left hand side, on the right it doesn't seem as defined at the waist on hips.
I have some great links that will help you with proportions and so on as you practice. You're doing wonderfully so far, so hopefully with a little guidance we'll make you a super Otaku yet :)
Oh, one more tip. Try using a reference image for pose and facial expression etc. Even if you're drawing anime, you'll find it will still have the same general shape - with a few differences in head to body ratio and waist/hip size.
Links:
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