Tennis
Sora initially started because of her mother's urging to quit soccer. While her mother hadn't meant to just find another sport, it was a nice half-way point for them both. She thought of tennis because of a fellow classmates urging to join the tennis club rather than the soccer club.
She was, at that point, tired of hearing how it was 'okay that she did soccer as a kid but what was she really expecting to do by persisting with it, there was no future in it' and was beginning to believe that there was truth to this. With all the current pressures around her she began to feel rather strongly that it must be her that's wrong if everyone disagrees with her so vehemently.
Regardless of the start, she really threw herself into tennis practice and enjoyed it a great deal. While she did miss the team playing of soccer (and often played doubles in order to make up for the loss) she really liked the freedom of playing one on one with someone. She wasn't supporting anyone and no one was supporting her, it suited her mindset at the time greatly and proved to help her handle the situations in her life all the better.
She had to become strong individually to win in tennis. It was the refreshing feeling of being independent that really enabled her to throw herself into the sport so much.
Despite this however she didn't have a great deal of talent for the sport, definitely not as much as she'd had in soccer, and so ironically had 'no future' in it.
This does not stop her from enjoying it intensely and practicing daily.