Robot Izonkei Joshi no Meiwaku na Nichijou

Hagane Takashina is a high school girl and a genius mecha pilot. For some reason, she confines herself to the cockpit of her robot. She doesn't even like to get out to go to the bathroom, so she wears diapers most of time. She loves her only friend, Kotoha-chan, so much that she would run through fire and water for her. Hagane is a clumsy girl who can't do anything on her own except pilot robots, but in order to pay off the huge debt from the damage she caused, she ends up doing handyman jobs ranging from finding lost dogs to exterminating ghosts with her robot...!

(Source: Kodansha, translated)