In episode 102, it has been stated that   is the most pure of all her friends, why is that so? And don't say that's because she's the main character! I mean all the other senshi have done things that were as pure, if not more than   .

Let's see...

  : Has a heart of gold, is sweet and caring to anyone, passed a great opportunity to study in a different country just because of loyalty to all her friends, is brave and whenever someone she loves is in trouble she stands up for them.

  : Sacrificed herself twice for    , got extremely mad and protective when   and her   where attacked by   , forgave   from her previous life and counsel her to make a new life and start learning loving herself.

  : Saved   from a group of thugs without even knowing her, putting herself at risk to defend    from bullies, cheers up   in the episode when   is targeted by the Death Busters, and sacrificed her life twice for Usagi.

  : Is an overall protective, caring, accepting, loyal and good natured person who will endanger herself to protect Usagi and all of her other friends.

And why is   the purest? What action made her stand out from the other 4 girls so much?

I'd have to say because of her the others are the way they are. In the beginning of the series you see Usagi is naturally happy go lucky. Full of life and warm energy. When first meeting Ami, Rei, Makoto, and Minako they all have this sense of loneliness. Each in every Sailor Senshi from their Galaxy were initially alone in one way or another. As their Princess and friend she was able to unite them and bring them happiness.

That's what I think of the most when it comes to something like this.

Lust wrote:

I'd have to say because of her the others are the way they are. In the beginning of the series you see Usagi is naturally happy go lucky. Full of life and warm energy. When first meeting Ami, Rei, Makoto, and Minako they all have this sense of loneliness. Each in every Sailor Senshi from their Galaxy were initially alone in one way or another. As their Princess and friend she was able to unite them and bring them happiness.

That's what I think of the most when it comes to something like this.

^ this basically. 

You could look at it from a perspective of: Usagi lacks darkness in her heart. She thinks of the best in people, including villains. She isn't malicious; she'd rather save the villains along with the rest of the world rather than kill them off or punish them. She has no bad bone in her body or malicious thoughts.

Usagi is warm, kind, and bright. Every villain basically comments on her shine and her warmth; that it is the brightest/warmest. This is due to that lack of darkness.

You make good points in that everyone has good hearts/traits, but she lacks the darkness. While they have good hearts/traits, they probably have a little bit of darkness within them. Just a little bit. It's what makes a human a human. Granted, Usagi is human too, but what makes her human is her flaws, which I totally embrace. 

Plus she is the titular character.

Sailor Mars wrote:

Lust wrote:

I'd have to say because of her the others are the way they are. In the beginning of the series you see Usagi is naturally happy go lucky. Full of life and warm energy. When first meeting Ami, Rei, Makoto, and Minako they all have this sense of loneliness. Each in every Sailor Senshi from their Galaxy were initially alone in one way or another. As their Princess and friend she was able to unite them and bring them happiness.

That's what I think of the most when it comes to something like this.

^ this basically. 

You could look at it from a perspective of: Usagi lacks darkness in her heart. She thinks of the best in people, including villains. She isn't malicious; she'd rather save the villains along with the rest of the world rather than kill them off or punish them. She has no bad bone in her body or malicious thoughts.

Usagi is warm, kind, and bright. Every villain basically comments on her shine and her warmth; that it is the brightest/warmest. This is due to that lack of darkness.

You make good points in that everyone has good hearts/traits, but she lacks the darkness. While they have good hearts/traits, they probably have a little bit of darkness within them. Just a little bit. It's what makes a human a human. Granted, Usagi is human too, but what makes her human is her flaws, which I totally embrace. 

Plus she is the titular character.

Usagi is love. She is all that is good and bad about love, but she is love and she is true to herself and her ideals, she is straightforward, and (anime speaking) she honestly believes that everyone can be redeemed. ^^

I think these are excellent responses I too, believe Usagi brought them happiness, and the girls themselves have confessed as well (as seen in Sailor Moon R movie) Usagi seems to be on a totally different level, especially in the final battle against Galaxia. I just can't imagine any of the other girls doing what she did, believing in the good inside Galaxia, even after she killed all her friends etc.

She believed in the Sailor Starlights, when noone else did. I think she's a really great character

Definitely a couple good points!

But am I the only one who found it odd that her heart was extra pure even though she slapped Mamoru less than 12 hours ago? Maybe her heart liked that?   Or perhaps they become extra pure on birthdays!!!

I always thought it was because of the silver crystal. We are going by sailor moon S logic, right?

To me she's the pure one because she has this sort of wide-eyed innocence to her... She's warm and loving and sees the good in everyone and INSISTS that everyone can be saved/redeemed. In S, Neptune and Uranus tried to convince her that her idealism was wrong and that they should just do the logical thing, even if it wasn't "nice". But Usagi just refused to harm Hotaru and nearly got the entire planet destroyed in the process. Usagi got her way, but really now... I sided with the Outers on this one ).

Usagi's basically a puppy. And I like to assume that the Silver Crystal is as powerful as it is in her hands because of her "pure" heart, not the other way around