Kuro Wanko to Kin Kitsune

Why does my heart hurt like this when Ren seems so happy with other people?

Saved as a cub, Yuki the golden fox has since grown up like family together with Ren the retriever in their household. Now, they both live together in the coffee house that Ren runs, but recently, Yuki's heart has been clenching a lot…?