Red Eyes

While the original Battle Dolls had Red Eyes it was gradually lost as the carbon element was introduced into their body with each passing generation. The manifestation of the Red Eyes in the current generation of Mibu represents the unification of mind, body, and soul. This fortifies their cellular structure slowing the progress of the Death Disease and multiplies their power and abilities several fold. Their "evolution" (or power up) are True Red Eyes.

Note
Red Eyes resemblese (in appearance) Naruto's Sharingan