Let's just get to spamming these short bios so I get all the designs out of the way, yeah? Yea.
This is Mu, who named themselves. They are currently the Vice Kido Chief under Eliot, formerly the 3rd seat when El was vice and her mentor Jeon Don was the grand chief. No one except the two proctors who allowed Mu into the Shino academy, Eliot and Jeon knows anything about them, including their gender or where they came from... or what they look like. All physical details except their height and thinness are known, since even when they remove their clothes they have a skintight, fullbody suit on at all times. People do know that Mu makes their own masks, and fashioned the current one after El's 'spirit animal', though she isn't quite sure what that means. Mu also was given permission to wear Jeon's old haori after he was forced to retire.
Now then, other than that Mu has had a pretty average career in the Kido Corps; in fact their odd pechant for covering themselves wasn't really odd in the formerly mysterious kido corps, though it is now. Some often mistake Mu for a visored.
Nationality: Unknown, though Zanpakuto has a Japanese name
Weight: 128 lbs
Build: Lanky, tall and thin, has large hands and feet
Distinguishing marks: Unknown
Occupation: Vice Kido Chief
Former occupation: 3rd seat, Kido Corps, 10th Seat, Kido Corps, Unseated, 5th Division
Zanpakuto: Ameki (Rain Tree), water type
Brief personality: Rather odd, though outgoing and talkative. Seems to have no idea why people think they're strange. Though they love to talk, they never seem to reveal any personal information, and their quick wit ensures oftentimes people don't notice this. Mu is very curious, though they sometimes seem quite naive, and when they hold someone in esteem they often go out of their way to please the objects of their admiration. Oftentimes it seems like Mu is quite young in the way they act, but there is an edge to their personality that few pic k up on that betrays Mu's intelligence and perception.