Ani - Imo.

兄が妹で妹が兄で。

Ani-Imo (Japanese: 兄が妹で妹が兄で。, Hepburn: Ani ga Imōto de Imōto ga Ani de; 'Big Brother is Little Sister, Little Sister is Big Brother') is a Japanese manga series written and illustrated by Haruko Kurumatani. Ani-Imo centers around Youta and his twin sister Hikaru.