S1 EP07 & S2 EP09
(please feel free to delete my commentary if you reblog!)
Until this moment, Rin had been hoping that he would be able to keep swimming with Haru while following his dream. That - just like he told Sousuke - he would be able to have both, his friends and his dream. But Haru has just made him realize that he had been too hopeful.
Here Rin is basically realizing that no; he may not able to keep swimming with Haru, after all. And it’s a really, really poignant parallel to the moment where Haru himself thought he wouldn’t be able to swim with Rin again - and his reaction to that.