One of the seven Level 5 espers, ranking fourth after Mikoto Misaka, she is the leader of the dark side team ITEM, which is at odds with SCHOOL. She looks down upon lower-level espers and does not mind eliminating people who get in her way or go against her, regardless of whether they are enemies or allies. Her cruel attitude led to Hamazura Shiage, a Level 0 who was ITEM's lackey at the time, to fight her to protect Takitsubo Rikou. Her overconfidence during that fight and Shiage's resourcefulnes eventually resulted in her defeat and mutilation at the hands of the boy and her own power. Becoming obssesed with Shiage after he defeated her, Mugino tried two more times to kill him, until eventually both she and Shiage made peace with each other during World War III and reunited in the new IT