He is protective over the cats that he knows and nice to them showing to them that there is nothing to be afraid of.
Roku is a large cat with brown and white fur, and olive green eyes.
He makes a very small appearance at the end marking his debut where Haru tells him that she is Hachi's older sister and thanks Roku for taking care of Hachi.
When Haru and Subaru went to Nana's house for visit to take the keychain off of Haru's paw, Hachi introduces Roku to Haru saying that he´s been there for very long. Roku then tells Haru that he can tell that she has been through a lot and that he will protect Haru and Hachi because they are family.