The original plot bunny:
at first it was just supposed to be a what-if high school reunion. Maya and Ichika were once in a relationship despite Maya being Ichika's homeroom teacher. They broke up because Ichika knew during his graduation, his life would become hectic and he wouldn't have time for Maya, so he broke up with her thinking she'd be unhappy from neglect if she stayed with him. Ofcourse Maya didn't take it well. Now the reunion would be the first time they meet face to face after 8 years.
The snow-balled stuff would be how they got together in the first place. Their first kiss(!?) random stuff