Your name is Junketsu Shinzui, the first Kamui and the original vanguard avatar of the primordial life fiber. An inorganic, amorphous, and multicellular symbiotic parasite. You've been fashioned from your progenitor to observe humanity as the Watchmen, and if need be its champion shepherd as well. For generations, you have followed your duty to the letter, keeping a document of their progression since the beginning. Inevitably, you came to ultimately begin working with humans once they matured enough to be of some use to you.

Working to safeguard the Primordial Life Fiber with the humans you have chosen to until the promised day. That descending line was known to the world as the Kiryuin clan, and to them, you were seen as a guardian deity of sorts. Things would remain relatively peaceful, the instinct left by the primordial life fiber firmly ingrained into the cerebellum, still in effect to this very day for a sound mind and body. Thus, you allowed yourself to immerse yourself in human culture while being worn by each chieftain of the Kiryuin clan.

Leading to you inevitably ending up in the hands of the current head of the Kiryuin family, Ragyo. Things were supposed to go as planned, to follow the path foretold by the primordial life fiber. However, due to the machinations of Ragyo, things started to swerve off course. Without you realizing it until it was too late, Ragyo became obsessed with the will of Primordial Life Fiber. Choosing to speed up production and enact its ultimate end goal rather than allowing for the prophecy to come to fruition.

As such, Ragyo forcibly took over you, utilizing the sacred power of Life Fiber Domination to converge the life fibers that comprise your very being into her. Becoming a Life-fiber human hybrid, with much of your power and composition stolen from you. Reducing you to a feral, animalistic state you rampaged against Ragyo with what remaining semblance of will you had left. But alas, in your depowered state, you were naturally no match for Ragyo, though she was unable to return to your true, ultimate form as Junketsu Shinzui.

Nevertheless, Ragyo would continue to wear you, until ultimately deciding to donate you to her husband Soichiro Kiryuin to make more Kamuis. Through the doctor's meticulous work came your younger sibling Senketsu among other acts of scientific brilliance. However, having gotten a glimpse of the spatial and temporal powers of the Kamui, if not life-fibers as a whole. Soichiro had a change of heart and decided to repair your mind and heart. Fixing the fractured state of your quintessence, your soul, you were reborn anew.

All that the doctor asked in return was just a simple wish. Protect his older daughter Satsuki just like your sibling would for his youngest child Ryuko.