It's weird considering the fact that our main heroine is baby obsessed, and roughly five years after graduation they got two kids. And her behavior is due to her mother's genes.
Very important news:
Most of the Fanbox extras aren't available by external means, so if anyone can (and wants) to support the author, you can sub to their Fanbox and contact me on Ko-Fi to translate the extras.
As far as I'm aware, they didn't meet each other until college (the chapter where they each other's yearbook photos shows this), so this may be a classmate of hers. The guy is older than her and got into college before her, hence the "senpai".
I can't access the Fanbox extras of a couple of chapters and the ones I have access to can spoil some stuff. I decided to just skip them and wait until I reach them so I don't spoil anyone.