The main themes of the show is a boy who now has a stepsister, his father is divorced from his mother and tries to make a good relation with his new family. However, Mitzuki (the stepsister) is trying hard to adapt this new style of life. After fainting in the street, she encounters herself with a Ghost girl who says that she needs to go to heaven, but first, she have to do some things before, mainly related to her new stepbrother.
This is a Romantic Comedy show, nothing intense besides strong Fanservice use happens. Nudity is the main factor of the series.