Looks good to my eyes. Reminds me of Shikamaru, who also had a carefree personality, though not sure about sweet. More importantly, he seems to be easily recognizable, unless other characters have similar buns and spiky sides. What I usually look for in a character, is for them to be recognizable at a glance. What they're doing, and what they may be feeling, and I think that was done well here. I think other details like hairstyle and clothes can adapt and change as the story develops, as long as the main silhouette still remains recognizable.
