I don't own Kure-nai.
On a hillside, there was the sound of somebody running. A girl of fourteen was running, carrying a five year old girl in her arms. The girl's name was Hotaru Kuhoin and her little girl in her arms was her little sister Murasaki Kuhoin, and they were running away from home.
The Kuhoin family had a tradition that all girls born in the family had to stay in a wooden building called the inner sanctuary with no light and had to stay there for the rest of their lives. And they had to give birth to their brothers children. Since Hotaru and Murasaki were girls, they had to live in the inner sanctuary forever and give birth to their brother's children. But they didn't want that, especially Hotaru. Hotaru hated the fact that she and Murasaki had to live in some sort of prison for the rest of their lives, never getting to experience the lives that girls her age would do, never getting to fall in love and live a happy life, and after giving birth they would never allow to be part of their children's lives.
Their mother Souju Kuhoin lived a bitter life full of sorrow, having to stay in the inner sanctuary and never raise her own children, both her sons and daughters, and that sadness caused her to commit suicide. Hotaru didn't want to live a life of bitterness and sorrow and she hated her family very much because of that. Same with Murasaki, she hated the Kuhoins too. So Hotaru decided to run away and take Murasaki with her. Normally no one could ever escape the Kuhoin grounds because there was bodyguards every. But Hotaru created a distraction so that no one would yet notice she and Murasaki had run away. She set the inner sanctuary on fire and now everyone was busy with dealing with the fire.
Right now Hotaru stopped running to catch her breath. "What's wrong Onee-chan?" asked Murasaki. "It's nothing Murasaki," said Hotaru "I just need to catch my breath for a bit then we can continue on running". "Will they catch us?" asked Murasaki. "No we will get out of here I promise you" said Hotaru. Suddenly there was a footstep behind them. "Who's there?" asked Hotaru, suddenly. A long haired brown woman stepped forward. "Benika, is that you?" "Yes it's me" said woman. Hotaru ran over to Benika. "Please help us escape" said Hotaru. Hotaru knew Benika because Benika had worked for the Kuhoin family and she was a friend of her mother. "That's why I'm here," said Benika "I promised your mother before she died that I would take you two outside. Do you wish to go outside?" "Yes we do," said Hotaru "I am not going to live my life the same way our mother did, and I won't let Murasaki live that way either". "Then come we must hurry" said Benika. Benika held Murasaki in her arms and she and Hotaru contined to run from the Kuhoin estate. "I must ask; what's that smoke from the building?" "I created a distraction to help Murasaki and I get away without noticing we are leaving" answered Hotaru. She didn't want to admit yet that she set the inner sanctuary on fire. They saw the outside of the Kuhoin mansion on a hill side. Hotaru scoffed and said that it make look beautiful, but to her it was disgusting. She clearly didn't want to go back there again and neither did Murasaki.
Meanwhile the servants had managed to put out the fire, but the inner sanctuary was destroyed. Hotaru's father Renjo Kuhoin looked at the situation and tried to find Murasaki and Hotaru. "Where's Hotaru and Murasaki?!" he demanded to a maid of the inner sanctuary. "We don't know sir," answered the maid "we lost sight of them during this incident". Renjo slapped the maid in anger. "You are in charge of watching them!" he shouted "how could you lose them?" The maid was lying though; she knew that Hotaru had set the fire to use it to escape. The maid was close to Souju when she was alive and she felt sorry for Murasaki and Hotaru for having to take their mother's place. "It was the death of Souju and the hate that Hotaru had for you that made her and Murasaki vanish" said the maid. Renjo gritted his teeth in anger and walke away in anger. He believed that Hotaru and Murasaki had runaway, so he had to make preparations to look for them and have them brought back.
By now Murasaki and Hotaru had left the Kuhoin grounds thanks to Benika and her helper Yayoi and they hoped to never go back there again.
If in Kure-nai that Murasaki did have an older sister there's no doubt that she would hate the Kuhoins very much and would take drastic measures to destroy the inner sanctuary herself. I'll explain of how Hotaru set the fire soon when she explains to Shinkuro about her family and past.