Tosa Nikki is a historical diary written by Tosa Yoshitada, a samurai from the Tosa Province in Japan during the late 16th century. The diary provides a detailed account of his experiences and observations, including political events, cultural practices, and personal reflections. It is considered an important document for understanding the social and political landscape of the time. The diary is notable for its candid and straightforward style, offering insights into the life of a samurai and the challenges he faced. It also reflects the broader historical context of the Sengoku period, a time of social upheaval and military conflict in Japan.