use this tutorial to cut out the anime character
http://paintdotnet.forumer.com/viewtopic.php?f=15&t=4841&st=0&sk=t&sd=a&hilit=cutting+out+images
and then inverse the selection (ctrl + i) and then delete and you should see a bunch of grey and white squares. the area with the squares with be transparent so it will show what ever you put behind it.
hope that helps!