Kanade

In the near future, an explosion of plant growth has left much of human civilization buried under greenery. Yuuto lives in a city largely reclaimed by nature. One day a girl named Kanade arrives at his door — they had been writing to each other since she found one of his carrier pigeons. She tells him she must sing the greatest love song in the world to save it in her mother's place, and asks if he would please fall in love with her. Warmly supported by those around them, the two begin to explore something they did not entirely choose — and discover a spark between them that had already started well before they asked permission.