A Tale of Six Trillion Years and a Night

The story tells of "a fairytale that no one knows" about a demon boy with no name, abused by the villagers, and who only wanted to be human. He wants to die, and he can't see any dreams in his future. One day, a girl named Ai comes to the prison he is held in. Although talking is forbidden, she asks him what his name is, and says that they will leave together. (Source: Vocaloid Synthesizer Wiki, edited)