Heisateki Imouto
Hitomi Asakura uses gorgeous draws to tell a story of how a little sister is growing confused & frustrated with her quiet love life, and how she asks her brother for a "little indiscretion", and thus how she can't deal with the strong feelings that flow after crossing such big line.
Narrated through the female perspective, while the story itself has much more sensibility than a mere "popular" Hentai, it's erotic theme is still the main focus. The short length of the story is actually a bad point, as it's particular story telling style & art could have easily made this an enjoyable, decent drama focused story.
Note: The chapter was originally published in in COMIC Megastore 1999-11.