Based on the adult maga by Yuzuki N'.

Akimasa is now a high-school student lives alone with his older sister who he obviously has feelings for "Mao-neechan". Aki's sister, for her part was pretty popular and well loved and responsible in school and is now a successful office lady... on the surface... but in reality she is much more troubled over Aki than what he will ever be over her... Can something possible develop between the two of them?

...Meanwhile Aki's Otaku childhood friend Rio and Aki's delinquent childhood friend Asami suddenly realize that they want to be much closer to Aki to what they are now.