The story started when the father of Yuuta remarried and he got a step-sister. Saki Ayase is the number one beauty of the school year. Both of them are not attracted to each other at first. They promised they would remain away from each other. Yuuta doesn’t know how to express his feelings to others and doesn’t know how to treat her. Saki is also unsure about the feelings and then they are at the same stage. They get comfortable in living together and this leads them to love. 義妹生活