i read from a comment somewhere that
R-18 has the same story line as
Momoiro Heaven, i've read both & i can say that it's not. R-18 has more cute not-really-smut parts while has Momoiro has fluffy ones. They're both high school love story & the female protagonists are both writers; those are just their similarities.
i like both~ yeah, i know i'm immature =.=