Daniel meets Azreal when he is 3 years old. Azreal knowing he will be punished for revealing himself to Daniel reveals himself anyways for he feels a connection to the child. This connection later on in Daniel's life turns out to be love. Azreal stays by Daniel's side as he grows to adulthood.
On his 23d birthday Daniel finds himself wanting to go back and change a moment in his life therefore asks Azreal to turn back time. Azreal questions him on it but in the end does as Daniel asks and turns back time to when Daniel is 14 years old.
The event Daniel changes is stopping himself from giving his virginity to a boy he does not love and in doing so Daniel unknowingly realizes he has fallen in love with his Fallen Angel protector Azreal.