(It feels...strange to have one of my students become my little sister...)
I, Makino Yuuichi, was thinking about this as I stood in front of the classroom.

Rokujou Girls' Academy, where I work, is known throughout the world for its prestigious status.
The reason I'm able to work there isn't because I'm an excellent teacher or have a good work attitude.
It's all thanks to my wife. Her maiden name is Rokujou. She's the granddaughter of Rokujou Academy's current chairman.
It was thanks to marrying her that I was officially hired at Rokujou Girls' Academy.

The classroom was filled with young girls.
They were all wearing the uniforms befitting a prestigious school, and (at least on the surface) they were all serious about their classes.

As I was reading from my textbook, I glanced at one of the female students.
Rokujou Minami, a bright, cheerful, and beautiful girl. She's the granddaughter of Rokujou Academy's chairman and my wife's younger sister. In other words, my sister-in-law.
Minami noticed my gaze and smiled happily.
If I wasn't married and a teacher, my heart would be beating fast.

I hastily turned my back and started scribbling on the blackboard.
(Maybe I'm overthinking it... But Minami's attitude lately...)