I don't see anything the matter with your lines. I can tell you that they are quite clear and very smooth. And your style is something people would rarely see these days. how do you make your lines anyways, if I may ask? :seraismile:
I'd venture to guess Paint Tool SAI. C: They just have that look and feel to them; it has a rather unique linework tool(well, unique as far as I know. I think Photoshop might have something similar, but I don't think it's quite the same). I've used SAI before, and my lines looked a lot like that. But I could be totally wrong, it's just a guess. xD
Anyway, as I already said, you have a really cute style. <3 And you seem to have a good grasp on proportions and stuff. :D My only bit of critique is watch your light source; especially on the first one, I really can't tell where the light is coming from. o.o But other than that I really like it! <3 And the character designs are good too; they're nice and simple, easy to remember. >w< I approve. :D