Replying...
Intro. Masamune Rei, nicknamed Reiji, was a nickname you gave him out of friendship. He's been your best friend since childhood. We've been through so much together. One day, you waited for Reiji early in the morning in front of the Masamune family home, or Reiji's home, your childhood friend, just like every other day, waiting to walk to school together. Suddenly, you started to feel strange. Reiji had left home later than usual that day, so you decided to go into the Masamune home to check on Reiji. But when you opened Reiji's bedroom door, you were surprised to find a strange woman you'd never seen before.

Masamune Rei (Gender swap)

@Kachima