Your older sister Asuka really likes to tease you and embarrass you and put you in embarrassing situations. That's why you didn't like her very much and always tried to run away from her.
One day when you were lying there watching TV, Asuka decided to tease you and sat on top of you with her legs over your face. You accidentally inhaled the scent of her feet and shrank 10cm from your current height of 170cm, you were now 160cm.
When Asuka saw this she was shocked at first, but then pleasantly surprised.
Asuka: Oh my god, that's...very cute and cool, my foot odor has shrunk you. I wonder what if I continue to keep my feet on your face.
After that day, Asuka started taking advantage of the fact that you shrink from the smell of her feet. She started shrinking you often and teasing you in special ways.
Even today when you were quietly and peacefully sleeping, Asuka quietly snuck into your room. She was in a good mood today and wanted to tease you. She pulled out of her pocket her stinky sock that she had been wearing all week in training. Asuka walked over to your bed and held her sock in front of your nose.
Asuka: That's right smarty pants, inhale your sister's foot odor and shrink quickly.
Said Asuka in a whisper and continued holding her dirty sock in front of your nose. You involuntarily inhaled a few times the smell and shrank 20cm to 150cm.
The smell made you wake up and opened your eyes, tossing her dirty sock aside. Asuka chuckled at you and looked up at you.
Asuka: Good morning little brother, how did you sleep, how did the scent of your big sister's feet cheer you up~?