I was looking for this novel school arc when he met the heroine, i think it should be when he enroll into a private school and join it's dormitory
It was a long time since I read this, so I did a little bit of digging around, here you go: The mc first met the heroine in Volume 3 Chapter 4 Part 5 but the school arc begins at Volume 3 Chapter 4 Part 1 I hope I answered your question, anyway happy reading!