Yuuichi has twin little sisters, energetic Miyu and tsundere Yui. They keep appealing to him at home and at school, but he doesn’t see them as more than his little sisters. One day, he peeked at Honoka changing in the literary club room and somehow it ended with Miyu and Yui joining the club as well. Then his father called him suddenly and revealed that one of the twins was not blood-related to him! Suddenly, he saw them as girls instead of imoutos. How will he be able to withstand their advances?