Hamekoi!

Most people have a secret they just can't tell others. For me, I have two. I have someone I like, and the other is... I am cross-dressing while attending an all-girls' high school. I, Mizuki Saiki, have an older twin sister named Miyuki: and she is practically forcing me to crossdress, so that I can attend her all-girls school as a female student in her place, to suit her own purposes. "This way, I can stay together with my beloved childhood friend Kaya-chan... as long as I don't get found out!" Earnestly trying to hide the fact that he's the only boy in a place full of girls... This is a comedy about a heart-pounding mission that's swirling with ulterior motives! (Source: Gangan Online, translated)