"When six billion people inhabit this planet, there's only one of you, at one place, at one time. Once is all I need, when you're once in my lifetime."
This was written in Hong Xiang's first love letter to Zoe. The two reunited at a gathering and subsequently fell in love because of a pomelo (notice the pomelo inserted in the movie poster). We don't exactly know the details but let's just say that's their fruit of love. ;)