Here's what I remember:
ML (who's been out of high school for about a decade?) time-travels back to his high school days to save FL from ending her life. I think she may have done it by jumping off the school rooftop, but I'm not 100% sure on that. There may just have been a rooftop scene where he confronts her.
I keep thinking the title is "Moment at Eighteen" which it obviously isn't, but I think it's reminiscent of that name. Maybe it has 18 in the title, maybe not.
It's either a short drama or drama special (also a chance it was a movie). I watched it around 2018-19, so came out before then.
