 Keichū developed an interest in traditional waka, (31-syllable) Japanese verse, including the verses in Japan’s most ancient extant poetry anthology, the eighth-century Man’yōshū. One feature of seventeenth-century Japanese poetics was an awakening interest in the anthology, but only about 10% of its 4400 poems were accessible to Keichū’s contemporaries owing to the arcane method of its original transcription. To remedy this lacuna the Daimyo of Mito commissioned a commentary, the responsibility for which, in a roundabout fashion, devolved upon Keichū. It was for that philological work that he remains best known.