Minis from Naruto are mini-Kyūbi, also known as mini-Kuramas.
They retain their canon counterpart's monstrous personality and aggressive tendencies, sometimes even towards agents.
Kurama is a gigantic demon with the form of a nine-tailed fox. Naruto Uzumki's parents sealed its powers inside Naruto as a child to prevent the beast from destroying their village. As Naruto grew and studied to become ninja, Kurama planned to make Naruto dependent on its demonic powers, hoping to eventually overwhelm him and break free. However, after watching Naruto's abilities and personality develop throughout the series, Kurama came to respect the human, and eventually allied itself to Naruto, allowing him to use its powers freely.