Touka Tsuyuri

Class Rep is one of Haruka's classmates who has been summoned to the Other World. Her real name has not been mentioned in the novels.

She is the leader of the Girls, as well as the de facto commander of any joint forces she became involved in. Sometimes she is called the "Translation Rep" because only she could get meaningful information out of Haruka's wandering ramblings.

(Source: Loner Life In Another World Wiki)