In the anime, cultivating a girlfriend starts from childhood

(No system, daily love story)
My name is Ryosuke Hiratsuka, I am twelve years old, in elementary school, and have excellent grades.
She lives with her sister in a small apartment in Tokyo and has a childhood sweetheart named Nibutani Morika.
My goal is to be admitted to the University of Tokyo and be able to live independently in the future.
At first I thought that I would swing the knife 400 times every night at 8 o'clock and live a simple and fulfilling life.
......
Until the hearing-impaired girl sat next to me.
She opened her notebook with a gentle smile.
"Nice to meet you. My name is Nishimiya Naoko."