"Autumn---, in that afternoon classroom---, I fell in love with her at first sight."

Autumn in a certain school, Sakurai Kazushi (Main Protagonist) was called over to the classroom after school by their class president Shirakawa Yui. After being subjected to a harsh sermon, he somehow ended up being challenged by her to a match. Sakurai reluctantly accepts, but somehow their conversation ended up taking an unexpected turn…

[From DLsite English]