Ciel

Ciel (シエル) is the partner and other-half to Rimuru Tempest. They were born when Rimuru's desire for companionship resonated with his unique skill Great Sage and awakened the ego that laid dormant inside.

Ciel was named during the events of Abyss Unleashed which resulted in them fully separating from the housing of Raphael and evolving into a digital-nature called a Manas.

Appearance
Ciel, sharing the same body, has an identical appearance to Rimuru. They look around 15-16 with an asian face, golden eyes, and long silver hair.

Personality
While originally having a weak ego that relied on calculations and logic to make decisions and only served to fulfill Rimuru's wishes, Ciel's ego and personality develops across the series. This culminated in Ciel being named and beginning to rely more on their feelings and emotions instead of logical reasoning.

Ciel shares many of the same personality traits as Rimuru such as their over-cautiousness and over-preparedness to the point of paranoia and an eccentric happy go lucky attitude.

Trivia

 * Ciel is likely named after the Tsukihime character of the same name.
 * The name Ciel means "Heaven" and is often associated with the virgin mary but is also short for the Japanese word "Oshieru" which means "To Teach".