Ryoma's Adopted Sister

After Ryoga was taken away from them the Echizen family was feeling down and depressed and in the end they decided to adopt. They were in America at the time they did and when they went to one of the adoption centers Nanjiro was enchanted by the girl with long white hair, he couldn't see her eyes because her bangs prevented it and when he did get a glimpse they were closed. The girl was maybe 2 years older than Ryoma and her play was amazing. He had chosen who he wanted to adopt. Years later they move back to Japan and start studying in Seigaku Ryoma making it as a regular on the tennis team and his adopted sister? Hmm I wonder..