Nagumo Sae is a young girl who happens to be the main male character's first love.

She suffers from short term amnesia, Meaning she can't remember things that's happened from when she wakes up. At first she tries to keep her condition a secret as she would like to be viewed as a normal healthy girl.. she always carries around a book with her, She calls it her ''Book of Memories''

Sacchan met with Macchan a long time ago right before he moved away with his parents whom he had forgotten. She had been waiting for him all along in the park while he had been way. She always has a nurse with her and if not right by her side she always watches over her.. As the nurse is a really though person to deal with at first she still sees her as a good person and a friend, while the nurse is like her guardian..