Toki wo Kakeru Shoujo, Hotarubi no Mori e Recommendations
Both are heart warming stories with sci-fi/ supernatural about a lively girl and her relationship with a boy. Both have a beautiful end.
Similar atmosphere. The artstyles are alike too, with bright colors and breathtaking sky frames. Both involve people separated in time and time tricks :)
Both are stories about the impermanence of love and friendship in this life, but also about the feeling that it is better to love and then lose because our memories of those time are eternal, or at least 'til we, too, pass on - both give a warm feeling of summertime and the bittersweet feelings of its passing...
Short anime movies that feature loves that under normal situations would not even be possible if not for sci-fi or supernatural phenomenon.
Toki wo Kakeru Shoujo has a sci-fi plot device while Hotarubi no Mori e relies on supernatural occurrence.
Both have an otherworldly, fantasy element where the life of a female lead is strongly influenced by the male lead, both have similar art styles, and they each have bittersweet endings.