Some little things I notice which you might be 
subconsciously seeing as "wrong" are:

1. Larva's eyes are red. (But I didn't know if 
you were going for artistic with the yellow 
highlights -- they look kind of neat.)

2. Larva also has pretty darn small eyes compared 
to many other characters in Miyu. The eyes are a 
tad on the big side here. Size-wise, I would more 
expect to see eyes like those on Miyu herself.

(2b. This will sound stupid, but. . . The eye on 
the right is more shaped in an expression I can 
imagine Larva having, where the eye on the left 
isn't so much. . . I'm trying to put my thumb on 
exactly what it is, but. . . *shrug*)

3. The mouth should maybe be a smidge to the 
right. You've got the outline of the face dead 
on, but the position of the mouth doesn't match 
it. (Or alternatively, you have the mouth perfect 
and just need to adjust the left hand line of the 
face. ^_^;;)

4. Larva's cloak is a bit blukier than you're 
drawing it. . . Don't forget it has a hood, which 
bunches up around his neck more.

5. I'm making the assumption you're aiming for TV 
Larva, but if you're aiming for OVA Larva, he has 
marks on his face similar to the tear-shaped marks
on his mask. (Not all four, though.)

But I like it. ^_^  I hardly see any fanart of 
Larva! ^_^

Many Sharp Smiles,
--Drac