>>2301646i think partially because makoto and haru's relationship mirrors rin's and sousuke's, in that makoto and sousuke both have a more talented friend who's always going to be just out of their grasp in some way. also makoto only started swimming because of haru and iirc sousuke also swims mainly because of rin?
so in the case that rin and haru ended up together (it's a shit pairing, but the series shoves it down our throats as hard as it can) they would both be left pining and could theoretically turn to each other instead. a lot of the doujins/fics play up the angst big time.
and they're also the two biggest guys and they look nice together. personally i think their personalities would mesh really well. someone, somewhere proposed the idea of them as a couple and it just got popular. (i like it because makoto can and should do better than that little shitlord haru and sousuke would treat him right)
sorry for the wall of text
