Two stories: As a child, Natsuki saw a gay couple on the beach, and it was his sole notice of them that made him realize he was different. Years later, he returns to the beach with his boyfriend. (There are more chapters about their love, how they met, and a beautiful rainy day at home.)
Their story continues in the book Kare No Barairo No Jinsei.
The second story is about a man who, fearing the end of the world, reconnects with a classmate he has admired for ten years. Their story is ambiguous, but I believe they will end up together. Some speculated they were the couple Natsuki had seen on the beach, but since their story takes place in 2012, I don't think it's possible given the timeframe and Natsuki's age.
Ringo ni Hachimitsu