Etsuko Sarutobi, nicknamed Ecchan, arrives as a transfer student at Mitsuba Elementary School, proudly declaring herself the 33rd descendant of the legendary ninja Sasuke Sarutobi and heir to his extraordinary legacy. Though outwardly unremarkable, she wields advanced ninja skills—superhuman strength, unmatched agility, and the ability to converse with animals. Her loyal companion, Buku, a talking dog offering sage advice, fluctuates mysteriously between communicating with humans and struggling to interact with fellow canines. Ecchan’s endearingly eccentric and guileless nature sparks humorous chaos, yet her intentions remain rooted in aiding those around her. Orphaned and adopted by her friend Miko’s family following a memory-erasing incident, her past before this event remains shrouded.

She navigates school life facing playful antagonism from classmate Ooyama, countered lightheartedly with her ninja talents. Her bonds extend to Taihei, the barber’s son; his younger brother Kurihei; and the empathetic teacher Ms. Shirayuki. Ecchan’s adventures intertwine mischief and heartfelt moments, from deploying hypnosis via pendulum swings or intense gazes—leaving victims with telltale swirled eyes—to rescuing mistreated animals or supporting peers through personal trials. The series culminates in an open-ended finale introducing Eiko, an American girl mirroring Ecchan’s appearance, who dreams of visiting Mount Fuji. Throughout, her lineage and inherited abilities anchor her identity, yet her journey remains grounded in the relatable turbulence of childhood, blending extraordinary feats with youthful misadventures.