A Week Of Indulging In A Once-a-year Physical Relationship With My Sister-in-law (brother-in-law) Who Has Returned This Year. Miu Shiramine

Once a year, my sister-in-law Miu comes home with my brother. While he's here, my brother ignores Miu and spends all day from morning to night fishing. Forgotten, Miu and I naturally grow closer, and ever since we crossed that line a few years ago, we have been indulging in a physical relationship during this one week every year.