Muaisou na Futago no Ane ga, Nazeka Ore to Naka no Yoi Futago no Imouto no Furi wo Shiteiru Hanashi

The main character has twin childhood friends. While the younger twin Rinka is cheerful and very lovable, her older twin Yuika is not quite the same. One day when he went to his promised date with Rinka, Yuika showed up as her?