I dunno if this is legit but s/he is Mian's weapon. Yep, s/he is a cyborg inspired from teen titan and kagerou project
S/He doesn't have a gender but Mian regards him/her as a "she" tho some people would think s/he as a boy.
ES stands for Eradicator System
Name (model name): ES-8364
Age: looks like 15
Height: 147 cm
Phobia: (Clasified info)
Weapons: S/He is a walking weapon
Likes: (Clasified info)
Dislikes: (Clasified info)
Personality: Doesn't understand human emotions. Only follow the program.
Sin: (Classified info)
Team: Team Fate I think since s/he is Mian's weapon
ES was originally from a private laboratory developing massive weaponry until s/he was hacked by Mian. Es was not a finished product, so Mian was the one to complete his/her system. Mian control him/her using his wristwatch. His/Her life is still unknown prior entering the laboratory."I need to gather more data."
This is what I get after watching Iron Man 1, 2, 3, Doctor Who, and Star Trek