As a jinchūriki of Shukaku, Mitsuko was feared by many of her peers, whose parents had recounted the terrifying tales of the beast they knew from the past. For this reason, Mitsuko made no friends in the Academy and grew up resenting the beast inside of her as well as many of her fellow students. Deprived of major bonds, Mitsuko instead focused on caring for her infant brother, with whom she became very attached. Sometime prior to Mitsuko's tenth birthday, her parents were both killed in the line of duty during a mission to the Land of Mountains. It is believed they were ambushed by criminal elements, but little could be confirmed from the crime scene.