Trying to figure out which theme you consider 'Nostalgia' since ... I can't find anything concrete for that one. This track on YouTube is what I'd like to do something for but on vgmusic it's listed as nostalgia, on youtube I've found it under Reminiscence and The Day Will Come, as well as one person in the comments of what I'm linking saying it is mistitled...
Edit: I should add, that on OCR's track listing for FF5, Nostalgia doesn't even exist.
Edit 2: Upon further digging... what a rabbit hole... it's under One Day, For Certain on OCR: https://ocremix.org/song/11108/one-day-for-certain