I finished a show which didn't reveal the incestuous element until its ending, Hensuki, two weeks and four days ago and although it wasn't quite what I was looking for I quite liked it. While the ecchi wasn't for me, Keiki's (Keiki is the protagonist) interactions with his sister were really sweet and her love for him came from how nice he was to her and from the time they spent living together; his sister didn't attempt to seduce him or do anything sexual but instead wanted a sweet romantic relationship. The lewdest thing she did was kiss him, and the lewdest thing she said was that her breasts were "unexpectedly large," knowing he likes large breasts, and nothing comes of it. The reason it isn't exactly what I was looking for was due to the majority of the run time being focused on other characters' perversions and the fact that they don't enter a romantic relationship so the concept of sibling romance can't be explored, with Keiki resolving to be her brother for now, although agreeing to his sister's request to go on a date with her for one day as her boyfriend, which I thought was quite sweet.