On his way home, Hayato notices a girl, Airi Kusunoki, running into the road while chasing a cat. As a speeding truck closes in on them, Hayato throws himself into the road to save them. He manages to save them both, but is left with fractures in both arms, requiring more than six months of recovery. Airi is extremely eager (and perhaps a little unhinged in her devotion) to look after him, so she decides to take care of everything for him. And she means everything.

Airi throws herself wholeheartedly into caring for Hayato, leaving him increasingly bewildered by her overwhelming enthusiasm as the two grow closer.