I dont think the shine looks that bad. Scanners are more merciful for acrylics...not so much on watercolours and coloured pencils.
Is it a direct copy from the manga cover or were you just inspired by it? Anyway the setting looks nice and the background is very interesting...but in my opinion you could have worked more on the shading and lighting. There's a nice orange glow behind the character but I wish it would go a bit further and affect his cape colour as well. And the shadows could look better with a blue tint since blue and orange are complementary colours. Great job anyway!