Ms. Nagisa or Nagisa-sensei is Ken's teacher. She is upbeat and enjoys teaching Ken and his classmates all about the technology of the era they live in. Their class takes way too many class trips and they always end up with Jurals attacking. Nagisa has also been a target of the Jurals as well, using her to get close to Ken.
She was brainwashed in episode 13 and ordered a worker robot to destroy an aquarium. Thankfully she was saved by Ken. Ken is usually getting in trouble for being late to class and causing other disruptions.