It is, but I like to start building the relationship early. Technically, I think of 'pre-slash' as "any story leading towards a romantic relationship but which doesn't end with them actually in one." Harry starts realizing he likes Draco in the second story, when Draco starts dating a woman.

And thank you! This story is one that won't work without powerful!Harry; I'm gleeful to have an excuse to bring him out to play.