Sage Transformation (仙人化, Senninka) is a bodily reaction exhibited by members of Jūgo's clan, caused by exposition of their special body fluids to natural energy. This results in increased physical capabilities similar to Sage Mode and the ability to perform various shape-shifting feats.
This transformation is a multifaceted ability that permits them to achieve feats ranging from creating various weapon-like appendages to even consuming other human beings, as well as a general increase in their physical capabilities, such as in strength, speed, stamina, reflexes, perception and durability, along with improved power of techniques. Once transformed, common features include eyes with yellow irides and black sclerae, altered skin colour and longer hair (hair colour change may also occur in some users).
In the experiments created by Orochimaru, this ability is referred to as "Cursed Seal Transformation" (呪印化, Juinka). A user of the Sage Transformation can transplant his or her flesh with anyone compatible with such experiments, in the events of a heavy injury, though this will cause the user's body to shrink in size and age.
Kabuto uses this transformation to enter Sage Mode.
Mitsuki can access this ability subconsciously to enter Sage Mode.
Jūgo's full Sage Transformation.
Kabuto's full Sage Transformation.
Mitsuki's full Sage Transformation.
The term "Sage Transformation" (仙人化, Senninka) can also refer to the transformation into the jinchūriki of the Ten-Tails.