Matsushita plays the role of the 29-year-old elder sister Fukazawa Hazuki who is meticulous, great at her studies but somewhat naive and not too good with seeking attention. She hopes to marry her boyfriend who is her colleague at the ward office. In addition, she holds a grudge against her younger sister who hogged their mother's love and attention when they were kids. On the other hand, Ishihara plays the 27-year-old younger sister Misaki who's lousy at her studies but is good at seeking attention and acting like a spoiled child. After graduating from high school, Misaki left home without a word and suddenly ends up at Hazuki's place without warning.
As the age setting of their characters are the same as their real ages and Matsushita has a younger sister while Ishihara has an elder brother, they both commented that it's easier for them to get into their roles due to the similarities with their real lives. Matsushita also praised Ishihara for being a cute sister while Ishihara commented that she feels slightly nervous in front of Matsushita because the latter is very beautiful.
Source: Yomiuri Hochi