Baku is good with a sword, but he rarely uses a hoof knife. Actually, he hadn’t used one at all until Nava appeared in his life. He found her in a terrible, neglected state. She was like a wildling, surviving alone in the forest far from civilization, afraid of people. That’s why the cat had to learn how to do hoof cleaning. Nava needed it! Nowadays, he sometimes cleans her hooves, but she’s become more normal and goes out more, so they wear down naturally now.
In any case, Baku looks smart in this drawing, but in reality, he doesn’t really understand how to use the knife. And Nava seems a bit shy, because nobody used to clean her hooves before — she never had to.