Having a Problem, Young Lady?

Tamaki, Shiina, Ayame and Minaha stay over at Shiina’s house to work on their new entry for the Summer Comiket, “Stardust Intenzione.” In the middle of the night, the doorbell sounds. Shiina opens the door to find Tamaki’s classmate, Natsu Iino. And Natsu has come to get her younger sister...?