Ore ga Suki nano wa Imouto dakedo Imouto ja Nai

Summary:

Suzuka Nagami is a beautiful third-year middle school student who has excellent grades and is the student council president. She wrote a novel about a little sister who dotes on her older brother, and the novel wins a light novel award. After they discuss the matter, Yuu is the one who debuts as a proxy light novel author instead of Suzuka, under the pen name Chikai Towano.

Summaries provided by MyAnimeList.net