I wrote a sequel to this fic. Here's the link:

Möbius
It had been years since the last time Dahyun talked to Nayeon. The last words Dahyun heard from her were "I think this is the end for us." Dahyun thought she would never talk to her ex again. But, Nayeon suddenly asked her to attend a career talk as a guest speaker at her former campus.

or

Dahyun still had feelings for Nayeon, but she wasn't sure Nayeon still had feelings for her.

or

Dahyun was trying her best to be Nayeon's sugar mommy. But, this might be a joke. So, let's find out yourself.