Kobayashi

Thanks, but I just read the synopsis of that episode and I don't think that's it.

The storyline of the unrequited full relationship is treated fairly sad/serious. Like you really felt bad for the male character. My gut tells me that it was chandler, so this had to happen previous to his relationship with Monica.

And the female character was definitely not Phoebe, Rachel, or Monica.

It was one of those female characters that was on one episode and we never see again.