Acid

Acid (アシッド) (real name unknown) is a member of Blue Blood and Counselor's twin sister.

Appearance
Acid looks identical to her twin Counselor; a short girl with silver hair tied in a ponytail, wearing a baggy dress shirt and leather boots, with her bare legs shown.

Toaru Kagaku no Railgun SS3
Acid and Counselor accompanied Sakibasu Ryouu to the building holding the corporate server of Zero-Day Link, and were tasked with preventing anyone from passing while she infected the server with Blue Blood's virus. They fought against Misaka Mikoto, Shokuhou Misaki, Shirai Kuroko and Hokaze Junko, and caused the group some trouble together, but were eventually defeated. After the fight, the two were bound and gagged before being put into random lockers.

Abilities
Acid is a Level 4 esper whose ability allows her to control oxygen.