Nat

Nat is a mi'qote, former coworker and ex boyfriend of B'eatriz, who met when they were both teenagers.

Nat is the product of years of experimentation, kidnapped when he was a toddler and originally had black hair and black eyes.

As he was the first to be experimented on by the assassins guild he was  taken by, he was also considered a perpetual failure, causing his hair  and eye color to change as well as losing most of the vision in his left  eye.

Despite this, others have an expectation of him to produce good results.

As a result of the pressure he is under, meeting B'eatriz his exact  opposite (naturally good at fighting, does it for himself and out of his  own volition) frustrated him. They had an unhealthy relationship for  about 10 years but B'eatriz did not know about Nat's backstory until  many years later.