Well, we all know how she was constantly "stalking" him. In fact, I would risk it and say Hinata is the cutest, most harmless expression of a Yandere. That, and also the fact that Naruto being outcasted is definitely not a secret. Her being too shy, or perhaps to scared to get any closer to Naruto when that's exactly what he needed might have been a huge disadvantage, but I think she's compensating now. Loving someone is scary after all. I know that the best.
In "stalking" Naruto, Hinata may have observed Naruto's horrid life and felt sympathy, but to assert that she understands his pain is grasping to far. True understanding requires a great deal of empathy, and in that regard Hinata does not understand Naruto better than any of the other Konoha 11, Sakura included.
Take Lee, Shikamaru, and Neji for example. Lee knows what it's like being thought of as a loser and having to work hard to get stronger, just like Naruto. Shikamaru lost his sensei Asuma, so he completely understood how Naruto felt when Jiraiya died. Although Neji was considered a genius, he was treated as a tool during most of his childhood, the same way that a Jinchuriki might be treated by it's villagers. None of them understand completely what Naruto has gone through throughout his life, but they all understand a different part of his pain.
Similarly, Hinata has a basic understanding of how Naruto felt during his childhood, though not completely. She knew what it was like being looked down upon, not by the entire village, but by her father. Does this mean that she understands Naruto better than any of the other K11? No. She somewhat understands part of the pain he went through, like many of the other K11.
At this point, I would usually also point out the regular argument regarding the fact that Hinata was apparently always watching Naruto. If she knew how he felt, I would think that she would have done something to get closer to him - to show him that he wasn't alone. She doesn't do that though. She's fine drawing strength from Naruto while watching him suffer, but she does nothing to return the favor to him. She doesn't even talk to him until the Chuunin Exams.
However, given your opinion, I'll let it slide.
Even so, she didn't try to get to know him personally, she just looked at the image he portrayed as determined and hardworking boy that she was able to draw strength from (The third databook also reinforces this by saying that "to her, he is the image of hard-work and potential). That's the image that Naruto portrays on the surface, but that's not who he is as a person. Hinata doesn't know the person beneath the image which is why every time we see her supporting him, she's always reinforcing his nindo. That's the only thing she knows to do because that's all she understands about Naruto. She doesn't know about his personal life of the struggles that he's been through with his team.
What does Hinata know about Naruto's relationship with Sasuke?
What does she know about his burning desire to rescue him from the darkness?
What does she know about his situation as a Jinchuuriki?
Unlike Hinata, Sakura was there for all of these things. She was part of Team 7 from the start, and has shared almost every experience that they've gone through together. She much better understands Naruto's desire to save Sasuke, because she shares that very same desire to save Sasuke make Team 7 whole again.
Even with things that she can't personally understand, such as Naruto's role as a Jinchuurki, she felt deep concern for him and had a desire to learn more about the Kyuubi and the Mokuton in order to help ease his burdens.
If we're going to talk about who between Sakura and Hinata better understands Naruto, I would have to respectfully disagree with your opinion.
Chatte is offline, I messaged her though, and I've invited a mother person. Lets keep it going guys this is great! Also, if you have ideas for the next one, I'll be trying to do this daily with help from L Lawliet, I'd love to hear them so shoot me or him a message. ^.^
