Tadakichi-san (忠吉さん), also known as "Mr. Tadakichi", is Chiyo's pet dog. A mild-mannered and gentle Great Pyrenees, he is large enough for Chiyo to ride on his back and indulgent enough to allow her to. Sakaki particularly likes him, because he allows her to pet him without biting her, something Kamineko has done at most. Sakaki also daydreams about being able to ride Tadakichi as Chiyo does.