A straight cat that currently visits Haru's house one day bites him. Haru wants to get close to the cat but the cat is quite surly and ends bitting him. In some way, that cat reminds him of Rin, so he named it like that.
I'm not sure if we're meant to believe this IS a cat and that Haru is imagining it as Rin because he misses him, or if this is actually Rin who is not speaking for...some reason. It would have made more sense as a recurring dream.