The song this was inspired from is "Kodou ~whenever~" from DNAngel (aka. Dark's theme)
I would call it 'Light in the darkness'

the song is a 'i'll be there whenever you need me' type song.
I figured that even though Kaitou Dark is, well, a theif (therefore dark)he is also a light in the lives of those he comes close to.
Plus i LOVE this song.
The overall picture is a happy one with darker undertones and meaning behind the initial image.

Enjoy!