The final four episodes of the Anime AIR. Sure, some may argue that it is a heartbreaking Downer Ending, but consider that Misuzu and her Mommy were closer to each other that one brief summer than most mothers and daughters ever will be in a lifetime.
The way this troper sees it, Misuzu could have had a long life of empty loneliness or a short one of deep love. The fact that she wound up with the latter was a triumph, and it's implied it broke her curse as seen by the kids at the end. Also heartwarming beyond measure: that Yukito is willing to sacrifice his humanity just to be with her for all of it.
The way this troper sees it, it's a Bittersweet Ending in that, yes, Misuzu does die, but thanks to Yukito, the curse she inherited by being a reincarnation of Kanna was broken. Same as the previous statement, except that it was never specified if breaking the curse breaks the chain of reincarnation, so Kanna/Misuzu should be happy in their next life.