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.
主角永见祐的妹妹凉花是一名成绩优秀的美少女学生会会长。她以筆名「永遠野誓」创作了一部“溺爱哥哥的恋爱喜剧小说”，获得了轻小说比赛的大奖并且出道。在妹妹請求下，祐成為了代理人，以「永遠野誓」的名義活動，身邊出現大量女粉丝。凉花以取材的名义和祐约会，虽然祐同意，但实际上祐只喜欢妹妹作品所描写的“妹妹”，而不是现在的亲妹妹。