Help me find yaoi manga

Help me please! The uke was forced to become a girl as a replacement for his twin sister(?). One day the uke and seme went out to river when the uke undressing and seme found that he's a guy, the seme run. After that they meet at high school. I've read this long ago but cant remembered the title sksksksks sorry cant help w the detail but I'll app if you help me find if you know ⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄