From xkazemg:
Tsubomi has always wanted to escape from the pressure exerted by her single mother. One day, she met a strange old man, who turned out to be the “grandpa” of the Ariake household. The Ariake family was actually made-up by a few “strangers”, each of whom played the role of a family member and Tsubomi-chan was to become one of the them! There, Tsubomi-chan has rediscovered the long-lost feeling of love and being loved.