Related Series Timeline :
1 Doukyuusei [Classmates] - Prologue
2 Sotsugyousei [Graduate] - Sequel
3 Sora to Hara - Spin-off (Story of Teacher)
4 Occupation to Beloved - Mixed
5 Graduation Certificate - Epilogue
6 Blanc (Last part of three series)
7 Futari Gurashi (Extras of the protagonists)
notice how they start with flip phone to current touch screen phone
This manga vol here focus on break up and reunite again yk
and MARRIAGE
blanc