🤔 in a way I can understand Kase if I think about Japan and how sexist and homophobic their society is. She isn't quite sure if she can open up to Fukami about her life, about her sexuality. Seeing how she is an athlete and her college and expenses are being payed by her sports status, be outed could destroy everything she did built. So she forces herself to only open up if she loose a race she is pretty sure she will win.
In another note, the author could write things more clearly and in deep so it would be clearer.
Either way, my interpretation is just that, Kase thinking about coming out.