Nee, Sensei summary:

This story is about a relationship between a teacher and his student, Homura. It just so happens that Homura's older sister Kaori was the teacher's first girlfriend. Back then, the teacher would always use Homura as excuse to run away whenever something happened and he would never get in the "mood" whenever he was with Kaori. One day, he saw Homura's exam paper and noticed that Homura wrote "I like you, sensei" in the upper right corner. Will he accept Homura's confession?