There are ancient creatures known as Sealed darkness which are demons made of darkness that takes the form of everyday animals they are born from the darkness, hatred or envy in people's heart with immense power and energy. The host with a sealed darkness can tap into the beast's power for his or her own power. However, using such power and energy can be harmful to the host, with the host's body and mind being influenced or even taken over by his or her demon. In Andre's case, when he uses the Kitsune's power and reaches a tailed transformation, the energy is so concentrated around his body that it constantly damages and repairs his body right away, possibly shortening his lifespan. Tapping into such unnatural power is very harmful to the host, as the host's personality gets suppressed by the animalistic blood lust of the sealed beasts and the intensity of power will harm the host if used for extended periods of time.