Fukasaku is a wise and elderly toad sage from Mount Myoboku in the anime series Naruto. He is one of the Two Great Sage Toads, along with his wife Shima, and serves as a mentor to Jiraiya and later Naruto Uzumaki. Fukasaku teaches Naruto the art of Senjutsu, helping him master Sage Mode. Known for his vast knowledge and strict, yet caring demeanor, Fukasaku plays a crucial role in guiding key characters during pivotal moments in the series.