Yukichi is the main protagonist of the The Masterful Cat Is Depressed Again Today series. He's a big as a human black cat who lives with Saku in her apartment.

Extraordinarily intelligent, he is able to walk on two legs and use any kind of tool or appliance. He also has a great memory capacity and can learn new things easily. He is very skilled especially at cooking, a skill of which he is very proud.

He takes care of the house while his mistress is at work, as well as taking care of meals and household chores. Although he claims to have bonded with Saku only to not starve it's quite obvious that over time he has grown fond of her, worrying about her health and supporting her in her daily problems.

(Source: The Masterful Cat Is Depressed Again Today Wiki)