Since her parents are a little bit slow, Matsuda Erika (or Eri for short) has taught herself to be independent and extremely reliable. Moreover, she devotes herself to taking care of those around her—even if some of her classmates find her behaviour overbearing and annoying. One day, a strange new transfer student is introduced to her class. This boy speaks in choppy sentences, has little to no facial expressions, and goes by the name Nogina Kaname. Instantly, Eri feels compelled to take care of this martian-like new boy in her class.