This is a Kurugaya origin theory. (it kinda got long).
Kurugaya had two parents, both brilliant. Her father was a champion martial artist and the her Mother a world renowned musician.
Her mother and father wanted Kurugaya to be the best so they persuaded her to do her best in everything. From her childhood Kurugaya was expected to be perfect in everything. Her parents only showed two emotions to Kurugaya. Whenever she did something disapproving her parents showed disappointment and whenever she did good they merely acknowledge it with an okay or a nod of head.
These robotic expression of yes and no was all she had in her childhood. She never interacted with other children and never understood them. Due to this she became emotionless.
One day she and her parents came to a small town when she was 10. There was a carnival nearby, her parents left her there while they attended some business.
She was loitering around for a while to pass time when she found someone. A boy was trying to climb a tree.
“What are you doing?” she asked him while being expressionless.
“Oh… Waaaa!” the boy fell as he turned “You surprised me.”
Seeing as there was no expression from her the boy replied to her question “When i was counting my money and fell my wallet flew from my hand and got stuck up there”.
Kurugaya looked up. Surely there was a wallet there.
“I was finally going to the carnival but now…” the boy looked dejected.
Kurugaya didn’t know why but she had an urge to help him. She jumped up and broke the branch holding the wallet. The wallet fell and the boy grabbed it.
“Thanks. You really saved me,” that was the first time someone thanked kurugaya. A smile threatened on her face. She felt her first emotion happiness that time.
“Hey do you want to go to the carnival? It’ll be fun,” the boy asked her.
“Me I’m not sure, my parents are…”
“I can pay for your rides too. I have enough money and this way i can pay you back, after all i wouldn’t have been able to go if it hadn’t been because of you,”
“Come on…” the boy pulled her hand but for some reason she didn’t show any resistance.
They road many rides any played many games on the stall in the carnival. It was the first day kurugaya had any fun. Soon the evening came and so did the time for Kurugaya to leave.
“I had a lot of fun with you today, thank you,”
“Um… yes” Kurugaya was feeling strange, she didn’t feel like this any other time.
“Hey. You look bad is something the matter?” the boy asked her.
“Nothing, i was feeling very good before but now that we’re separating i feel… odd.”
The boy stared at her for a minute and then said “wait here for a moment.” he said and ran off. He returned in a few minutes with something.
“A ribbon?” in his hands lay a yellow ribbon.
“Yeah, you know you looked sad at the prospect of us going away so i brought this.”
“Because i looked sad?.”
“Yeah, my mom told me that yellow colour is for happiness and hope. I am giving you this because i want you to become happy again and also you can hold hope that we meet each other again.”
The small act of kindness. It was something foreign for kurugaya. She didn’t know how to react.
“Should i tie it in your hair?” Kurugaya just nodded. The boy clumsily tied it on the left part of her hair.
“Sorry I’ve never tied a ribbon in a girl’s hair before.” it was time for goodbye now “I’ll see you again bye-bye.” his words were like a promise to kurugaya.
The boy said and ran away in the drowning sunset.
That day kurugaya felt happiness when she helped him. Fun when they spent time together. Sadness when they separated and… an unknown emotion.
Those emotions were now only left in Kurugaya’s memory. She tried to replicate them but she couldn’t. So she put on fake emotions and tried to recreated them with other people, but they were always either kids who saw her as odd or those whom she didn’t had interest in.
A desire was born in her heart now, That she can put away these fake emotions and once again experience the real one’s. It was only fulfilled when she met the Little busters.