Bambi

This manga and Astro Boy sort of represent a maturation in Tezuka's art, and style. You can really sense a level up from his earlier works and the shift to a full story with narrative complexity. While Mimio's story also had depth it lacked the ups and downs of Bambi. Whether it was Taluka's passion for the source material or years of having drawn animal inspired manga, the characters pop in a way that his previous drawings didn't. I'm unsure when the color version was created but it was incredibly well done, and the shift of different base colors through the seasons was a nicetouch.