Amatsuka Miku

The protagonist's, whom she calls "Nao-kun", childhood friend who lives in the same apartment. She is also Saaya's best friend.
Miku is a very positive and an innocent girl who is always smiling and able to befriend pretty much anybody.
Because she lives by the motto of "think more about others rather than yourself", she is always ready to help people in any way and do things for the others. However, both the protagonist and Saaya would like to something for her instead of always relying on her.