I really like this story because there's so many ways it can go.
1. Eventually they do part ways, a friendly break-up as they leave school. The guy would always carry the memory of this.
2. Maybe in inches, she becomes less uncomfortable with men and needs to transform him less often. That would need to be carefully written not to come off as promoting gay conversion but if written carefully it could be cute. They stay together
3. The most obvious and personally appealing route, they become a true yuri couple and the transformation becomes permanent.
TS yuri is some of my favorite thing. If yuri-purists don't like it or don't want me even calling it yuri, they can suck my dry yellow toenails. This is super cute and it's between two physical girls.