The single was written and composed by YUI. She said that she attempted to make the song sound pop-like, while trying to add a slight pizzicato which she picked up from the atmosphere of Paradise Kiss. She also said the song was one of deciding to prepare oneself, while finding answers as you mature.
The A-Side "Hello (Paradise Kiss)" was composed to be the theme song of the live action movie Paradise Kiss based on the popular manga created by Ai Yazawa. The B-Side "You" was composed to be the ending song of the same movie. The first press editions came with original illustrations by Ai Yazawa and postcards were also included for some customers in Japan.