a is still figuring out how to interact with his new stepsister, Saki Ayase. After discovering they have more in common than expected, the two reach a comfortable equilibrium, but things start to get out of whack when Saki fails one of her exams and asks for Yuuta's help. Then Yuuta's attractive college-age coworker, Shiori, invites him out on a date, and Saki finds a strange new emotion welling up in her heart...Just what is this feeling?