well I can find you some more stepsibling shoujo but they're not smutty...I haven't found a lot of smutty shoujo...but if you still want some that are similar I can hook you up...marmalade boy is similar...weirder and I don't think its good cause Akuma De Sourou is a bit unique but I can help you find some...
ummm you might like Ai Hime Ai To Himegoto they are not step siblings but he's her father's adopted brother. So it kinda has a forbidden love sorta feel but not much...she's never met him and he was adopted in like his late teens and only lived with the family for a few months...so I didn't really have any problems with the relationship. It has a similar teasing male, innocent female. Its very sweet and a favorite.
http://myanimelist.net/manga/766/Akuma_de_Sourou/userrecs reccomendations for akuma de sourou on myanimelist...people tell you why they're reccomending. You might check it out
Hey guys!!! I've read this really good manga called Akuma de sourou, it's a really good stepsister/stepbrother romance with an amazing plot, I was just wondering if there were any good mangas that had that kind of romance with the siblings, but it was a bit more smutty (mature) and nice art? PLEASE HELP