If you liked the Himitsu no Shitsuji-kun manga, the Anime-Planet community thinks you'd like:
Both by the same mangaka, the short stories of Himitsu no Shitshuji-kun have the same sort of feel and style as Atsu Atsu Trattoria with the enough enigmatic bishies to keep all fangirls happy. The style isn't too sickly sweet for more mature readers but also not full of smut. If you like one give the other a try!
Two similar sets of shoujo romance stories, Kara no Shounen is the more tragic of the two (and perhaps better paced) but both give you that warm, naive feeling that any shoujo fan demands. Also the art in both is really attractive. (YAY Bishies!)