Izumi "Mustang"? Not one of the most common theories, but very interesting. You should write more, though it makes a good one-shot.

The theme is unique, I must say. I like the potrayal of young Izumi. If every stair is a secret, then Dante's house is full of secrets )

Roy as Izumi's little brother? Weird.. but I would love to read a story like that. Youve got my otes. Great job prtraying a little Izumi... i love it

Very nice little ficlet. I'd love to see something longer focusing on these two.

Roy and Izumi as siblings? Didn't see that one coming, but okay. ;;

Roy-as-Izumi's-little-brother theory?

I so want to make a crack drabble out of that. Ahem. On to praising your writing, which is what I'm supposed to be doing...

I at first thought Izumi was kind of OOC, but then I thought again about her age and realized she probably wasn't that confident when she was so young. I liked this because she reminded me of Ed in this fic, with how she's so fascinated with alchemy she forgets her other problems and gets lost in it.

And yes, there are secrets in Dante's house, aren't there?

Thumbs up.