Disclaimer:- Don't own, so don't sue.
Authors Note:- Please R&R!!

The Sailor Scouts had all fought their own demon when Nat arrived on the scene. Nat was the newest member of their party and also the youngest (apart from Chibi-Usa, but she's not there any more.)
"Nat!" Cried Serena, before she fell to the floor. "Help."
"No, we can manage." Raye said whilst struggling to stay standing.
"Yeah, sure you can." Nat mocked, noticing that all the other Sailor scouts were almost unconscious, she knew what she had to do.
"Sailor Scorpio Star Power! Make-up!!" Nat transformed into Sailor Scorpio.
"Nat, don't, you'll get hurt." Mina said weakly.
"I've got to, you guys are the only friends I've ever had. Scorpion poison hammer sting!" She leapt into the air and sent out a bolt of jet-black lightning. It hit the demon and sent it flying, but unbeknown to her, didn't kill it. "See, I told you I wouldn't di…!" She was cut short of breath by a giant tentacle coming up and grabbing her round the waist. Struggling, she managed to free a hand and hold on to the tentacle tight. Summoning up all of her remaining energy, she transformed into Star Sailor Scorpius.
"Wow." Breathed Serena, and her and the other scouts watched awe struck as Star Sailor Scorpius used her most powerful attack.
"Scorpius wild death scream!" Nat yelled. A shock wave ran through the earth and exploded in front of the demon that promptly let her go. Then the most un-earthly scream filled the air and a jet-black cloud covered the demon. There was a small explosion and the sailors felt their energy returning. Nat landed on her feet and grinned. She received a hug from all the scouts.
"Hey, Nat," Raye said, "Thanks." Nat grinned.
"It was nothing. Honestly." Suddenly a black thundercloud formed over them, there was a strong wind blowing around Nat.
"What's going on Nat?" Mina asked as Nat was lifted up, a look of absolute horror on her face.
"My time's up." She said, in a voice barely above a whisper. She was engulfed in the black cloud and there was a mini thunderstorm, but without the rain. After a few minutes, the cloud lifted and Nat was lying on the floor, almost dead, holding her most treasured possession, a gold mirror. The sailor scouts all rushed to her side, and Mina propped her head up on her knee.
"No…" Sailor Moon and Sailor Venus said almost in perfect unison.
"Mina, take this, my mirror. Whenever you need me, I'll be there." Mina nodded and took the mirror. "Remember the battle is not over yet and you must survive and continue living your life to the full." She drew in a deep breath that obviously caused her a lot of pain. "I failed you all, I'm sorry."
"Shh. No, you didn't, you saved us. Serena, can't you do anything?" Serena shook her head.
"I'm sorry Mina, I failed you sis. Don't ever forget me." And with that, Nat died.
"No!" Mina put her head in her hand and sobbed. Raye came down and sat next to her.
"Come here." She gave Mina a comforting hug and reassured her that it was going to be all right. Shakily, Mina stood up and looked in the mirror. She didn't see her reflection, but she saw all the fun times her and Nat had together. Ami put her hand on Mina's back and said, "Let's go home." Mina nodded and looked over at Sailor Moon who was also crying. They formed a circle with Nat in the middle and teleported home. They put Nat's body in the morgue and went to tell her mum.
"What'll we say?"
"That we found her. Coz in a way, we did." Serena said simply, tears running down her face. Mina felt a funny jolt from the mirror and saw Nat and her as youngsters, playing she was right, they were sisters. Mina started to cry again and as she couldn't bear to see Nat's mum, She shakily walked off home. She ran in and went up to her room. Artemis knew something was wrong.
"What's wrong Mina?" He asked timidly.
"Oh, Artemis, she's dead, Nat is dead and to make it worse, she was my sister!" She sobbed into the pillow and Artemis put a paw on her back.
"It's okay, everything's gonna be alright."
"No it's not. Nothing will ever be the same again!" She continued to sob into her pillow until she fell asleep but even then, she dreamt about seeing Sailor Scorpio, Nat, die trying to save her and the rest of the Sailor Scouts.