Writer's Note: This is the backstory of Ammy. I recommend reading after you finish The Third Child. Spoils the series otherwise.
A baby cried out in the rising sun. Akira grunted, and Inutaisho bent down to help her. "She's beautiful," Akira said, "what shall we name her?"
"She was born in the light of the rising sun. We shall name her Amaterasu."
"Yes, Amaterasu. And she will carry the legacy of us both."
"That she will. And we all will feast as she brings honor to the family name..."
Skip forward 30 years(Amaterasu matured by 10 years)…
"Amaterasu! Turn back!" Inutaisho shouted, the sounds of war echoing around them.
"But Father~! Sigh…" Amaterasu said, heading back, grabbing a standard blade for defense. She headed to the wooden shack containing medical ointments and bandages. A few yokai were already there, being tended to by crippled or weak yokai who did not wish to fight or were unable to. She sighed and said, "How can I help?"
"We've got it here. Why don't you go out and help the fallen?" a purple serpent said.
Ammy headed back outside, her eyes coming upon a terrible sight. Her father's Tetsusaiga clashed against the fearsome blade Masenko, wielded by the enemy commander, the nekoyokai Ryota-Hihi. Ryota-Hihi saw her come out of the shack. He drew back and rushed toward her. He drew his blade and went to strike. But Akira dashed in front of her in the last second. "Mother! Please be okay, please be okay, please be okay,.." Amaterasu said, her mother collapsing in her arms. She kept saying "please be okay" but inside she knew it was a fatal blow. Akira said, "Looks..like I won't..be able to..feast with you..Inu..taisho.." she said, then went limp in her only daughter's arms. Tears ran down her face. She set her mother's body down gently, then stood up. There was a ferocity in her eyes. Ryota-Hihi chuckled. "You're a child, you can't seriously think you can beat me!" Then he stopped. "Oh no you're serious." he whispered, before Amaterasu's eyes gleamed. Her father stood by her. He handed her the Tetsusaiga and said, "I know you can wield it. You've been more than ready for far too long."
She accepted the blade before sinking into a fighting stance. Ryota-Hihi stepped forward, his eyes filled with hatred towards her entire family. Amaterasu dashed forward, slashing Ryota-Hihi across the chest. He kneeled and said, "Fall back, my armies. We have been defeated in battle, so we shall leave your territory peacefully."
"Father?"
"Yes, Amaterasu?"
"May I also suggest further action regarding this?"
"Yes. What would you like to suggest?"
"I propose a peace treaty between us and our adversaries, so we may avoid further conflict and prevent further-" she paused, "casualties." Everyone was taken aback by this, but Inutaisho's eyes gleamed with pride.
Inutaisho replied, "I think that's a fine idea, Amaterasu. What do you say, Ryota-Hihi?"
"I agree. May we also tend to our wounded?"
"Of course." Inutaisho said, with a nod.
After tending to the wounded(almost done)...
"You didn't have to bandage me up, you know." Tsukuyomi, Ryota-Hihi's son, said.
"That's ridiculous. We both know your arm was wounded, and all the healers were tending to other yokai." Amaterasu replied in a calm voice, continuing to wrap his arm before tying it off. "There. Hey, before you go, do you want to sit down and talk a bit?"
"Ok, sure." They sat down. "So, you're Inutaisho's daughter, right?" Tsukuyomi said. She nodded. "Wow, I guess we're in the same boat. But is your father strict, expecting you to be great at everything?"
"No, not really. He scolds me when I screw up, but only if I knew it was wrong. Whenever I do something bad but I didn't know, he just explains to me what it is I did wrong. So your father is strict?"
"Yeah. He explained to me a few times in the beginning, but now he knows I'm talented, so he expects me to know everything and be good at everything. It's kind of overwhelming sometimes."
"Huh. Do you have any abstract qualities?"
"Yeah. I can do this weird thing where my eyes go red and three tomoes appear in them. I asked about it, and it's called the Sharingan. Apparently it comes from my Uchiha lineage. And I can use it to copy the abilities of anyone I meet. What about you?"
"I can summon huge draconic skulls that fire lasers. Noone I asked knew what their name was, but one day the name came to me. So I call 'em Gaster Blasters."
"That's a nice name for them. Can I see them?"
"Sure." She pointed out her hand. Draconic skulls appeared in the air. A high-pitched whine filled the room, and they opened their mouths and shot out a bright cyan beam, obliterating the wall.
Intaisho came over, looking mad. "What did I tell you about using those things indoors!?" he shouted.
"Sorry, father.." she said, hanging her head.
Skip forward to Izayoi's time…
Amaterasu stood there, watching the soldiers fire arrows at the mansion. She felt her father rush over her head, and heard Myoga trying to discourage him, to no avail. Sesshomaru came up behind her. "Wish he would've let me do it. At least I could teleport in, grab her, and teleport out," she said to him.
"Oh, come on. You've said yourself before that you would change the timeline, or whatever it is."
"I know. But at least he wouldn't get hurt."
Suddenly, the sound of a baby's cry reached their ears. And the sound of swords being drawn. "Ammy, no. You're not going in there," Sesshomaru intervened. Izayoi rushed out of the burning, unstable mansion, their baby brother in her arms. Amaterasu tensed. They scented blood. And heard their father's yell. "Inuyasha. That is the boy's name. Protect him, Izayoi." His sword clashed with the samurai's.
Amaterasu tensed, but her brother's arm stopped her. Izayoi rushed to the village.
In the aftermath of Inutaisho's demise…
"We have given the Tenseiga to Sesshomaru and sealed the Tetsusaiga within Inuyasha. What shall we do with the Sounga?" Myoga said.
"Giving it to Sesshomaru is too risky. He would likely abuse it's power." Totosai replied.
"I'll watch it for about 800 years or so." Saya said.
Ammy walked out of the shadows. "There's no need. I'll take it myself," she said.
"Amaterasu. I know you must feel left out. But are you sure you can control it's power?" Totosai said, "After all, you are not a full yo-"
"Do I look like I care!? Why should it matter if I'm a full yokai or not!? It depends on the person, Totosai!" she shouted, crossing her arms.
"Okay, Amaterasu. But if you cannot control it's power, do not blame us for what happens."
