6 years ago.
In an apartment, there lived a happily married couple with two girls as their children. One is a 12 year old girl while the other is a 6 year old girl; they share the same characteristics of having dark purple hair and light blue eyes, although the older sibling has short hair while the younger sibling has long hair. They were playing together with their toys, mostly blocks and airplanes.
"Dinner time, my dear! It also includes you, Keiko, Misao!" called the mother.
"I'm coming!" yelled the three.
Upon getting into the kitchen, they were enjoying their dinner of roast chicken with some vegetables.
"So, Keiko, how's school?" asked the father.
"Good, Dad, it's great. I got my report card," replied the older sister in a happy way as she shows her report card and gives it to her father. "It has straight 5s."
"Wow! That's very good of you. We knew we can count on you, right, Shigeki?" the mother said.
"Come now, Kotoe. We can also count on Misao, right?" the father asked as he and the others look at her. The look on her face is shy and she gives out her report card. Upon taking a look at it, she has straight 3.5. "Oh, better luck next time, Misao," he then shows the report card to his entire family.
"Yeah, better luck next time, Misao," Keiko said as she chides her for her the way she gets her grades. Her sister looks all shy and embarrassed, but it's time for her to be serious about this. "Hey, don't be embarrassed. You did good despite all that you did."
"Really?"
"Yes, really."
The two sisters then smiled on to each other as they have each other to count on.
Trouble looms into that fateful night. Misao went out of bed to get a glass of water from the kitchen. She witnesses troubling in the living room as she saw her parents being all injured and covered with blood. In the center of it is Keiko as she is holding a kunai; therefore she is the one who did this.
"Keiko!" she cried.
"Well, hello there, Misao," the older sister looked at her with no emotion from her face.
"What did you do to our parents?"
"I attacked them."
"Why?"
"I wanted to test out if you're truly worthy of surpassing me. Oh, and don't worry about father and mother. They're still alive."
Misao can't believe what Keiko has done to their own parents. She happens to be scared at her mind for this moment to come back.
"Look at you, dear sister," the latter stated. "You are so weak."
"No, I'm not weak!" the former cried back.
"Really? If so, I dare you to hit me with your fists."
The little sister clenched her fist with her right hand and started running towards her big sister, but the former blocks it and throws her to a wall with a punch. Despite this, Misao attempts to make another fist, but Keiko punches her to the face and throws her to a wall.
"Do you why you're weak, Misao? It's because you spend most of your time being shy and not opening up your true feelings for anyone. No wonder why you got 3.5s in your report card. Well, if you want to beat me one day, then learn how to be open. You gain more power than you can possibly imagine, but there is a price. You must kill your best friend. As I have. Come and seek me out, some day, when your power surpasses mine. When you opened more of your heart," the latter said as she left the apartment with Misao being all traumatized by this moment. She just can't believe her own older sister has gone evil and attacked their parents like that. Reminding of her words, Misao swears to do what her sister tells her to do and hopes to beat her the next time she sees her.