The picture book series, published by Kodansha, Ltd., has been released in Japanese in seven volumes.
ðə pˈɪktʃɚ bˈʊk sˈɪɹiz, pˈʌblɪʃt baɪ kˈoʊdænʃə, lˈɪmɪɾᵻd., hˈæzbiːn ɹᵻlˈiːst ɪn dʒˌæpənˈiːz ɪn sˈɛvən vˈɑːljuːmz.