Hakuunsai Tozawa is an amiable elderly mentor residing in the mountains, distinguished by his long white hair and a chokuto sword concealed within his cane in shirasaya fashion. He encounters the dedicated youth Sasuke Sarutobi in the Togakushi Mountains and agrees to train him. For three years, Tozawa instructs Sasuke in martial arts and ninja magic, including the Ankoku toshi jutsu (darkness perception/penetration technique). This rigorous training transforms Sasuke from an eager novice into a skilled practitioner ready to face supernatural threats.

Tozawa's teachings specifically focus on harnessing magical abilities for combat, preparing Sasuke to battle the demon witch Yakusha. This involves physical techniques and strategies for supernatural battles, such as fluid transformation fights where magical energies clash. His background connects him to Koga Ninjutsu traditions. Portrayed as a secluded master, his pivotal guidance enables Sasuke's final confrontation against evil forces. Tozawa consistently serves as a wise instructor across his appearances.