The legitimacy of manga adaptations into anime depends on several factors. Sometimes, they stick closely to the original plot, characters, and art style. But in other cases, they might make changes to fit the animation format or to add new elements for entertainment value.
The consistency depends. In some cases, the anime sticks closely to the manga, but in others, there might be changes in plot or character development for various reasons like animation style or time constraints.
The Naruto anime is widely regarded as a faithful representation of the manga. It manages to capture the key elements and excitement of the original. Although there are some differences to accommodate the medium of animation, they don't significantly impact the overall experience for fans of the manga.
Overall, it depends on the specific manga and anime. Some maintain a high level of fidelity, keeping the plot, characters, and themes intact. However, others might make alterations to fit the animation format or for creative reasons.