Nagami Yuu finds out that his little sister Nagami Suzuka - who is her highschool student council president - wrote a light novel titled “The Story of the Little Sister Who Loved Her Older Brother so Much it was Troubling“ on a whim under the pen name “Eternal Promise“, and won an award. He is a bit taken aback at first, because he had been submitting light novels to contests for years without winning an award, but agrees to serve as her strawman by posing as “Eternal Promise“, so that their father and her school won’t find out about her new part-time job. But it’s not like she likes her brother, or anything!