I don't know if you like old movies, but I'm going to recommend these just in case:
- Floating Clouds (the FL in Narratage actually watches it at the theater at one point): it's actually requited once, during what might be arguably the happiest time for both leads, but then they returned to Japan and they kept meeting each other in the hopes of regaining that happiness even though it's impossible
- Yearning: the FL got confessed to by someone unexpected (and, in her mind, impossible), causing her (and him) torment
- Happy Together: a gay couple from Hong Kong moves to Argentina to start a life together, but selfishness and the tendency to self-sabotage ruins their chance to be happy together
- Akitsu Springs: a starry-eyed young woman and a depressed young man get together in the titular spring; they continue their relationship for years because she sees him as the love of her life, even though he only ever considers her as someone "convenient"
