Zoku Shishunki Miman Okotowari summary:

Asuka, who lived in Hokkaido with her mother, moves to Tokyo to look for her father she has never even met before. When she gets to his house, he is not there, only his children, who claim they have never met their father either. Asuka decides to stay with her "brother" and "sister" while she looks for their father. Her two "siblings" are living alone and things sorta get complicated when Asuka and her "brother" start to fall for each other...