Shibasaki's character Hikari is the wife of Yasuda Masazumi (Higashiyama) who is a popular newscaster and goes all out to support her husband in every way. She is great at household chores and is able to make her husband look good in front of others. However, there is a secret between them thus explaining why the title doesn't explain what kind of wife she is and that will be explained in the first episode. Filming for the entire drama had been completed.
Shibasaki commented in an interview that her roles so far had been more focused on the emotional side of things but this time, she had to deal with a huge volume of lines so it was a fresh challenge for her. Besides, there was a constant struggle between emotions and common sense in the story which made it a tough battle up till filming was completed. Despite the fact that Shibasaki has been the lead in many movies to date, this is surprisingly her first leading role in a drama series. However, she has never thought much about this because she doesn't think of movies and dramas as totally separate things. It was also great this time that she got lots of support from the people around her and it was good that they didn't have to film as the drama is airing so it took off a fair bit of the pressure. As for her first time playing a housewife, Shibasaki admitted that she was looking forward to becoming a housewife one day when she was young but she doesn't feel the same way now.
Source: Yomiuri Hochi