Ruru Sanjo
Ruru Sanjo, more often referred to as "Baa-chan" ("Granny") by her tenants, is the tough-as-nails, pistol-packing landlady of the Gochiso apartments, which double as a school supply store that she also owns. Impressed by Hibiki's strong determination, she offers to help him in his mission, helping him disguise himself as a woman and maintain the disguise throughout his time on campus. Spoiler In the final episode, it is heavily implied that Ruru is a crossdresser as well. (Source: Wikipedia)