Zashiki no Nonono

Top national exam scorer Horikoshi Tsuyuko found a little girl tied up in the sealed closet in her house, and this girl, Nonono, is a Zashiki warashi? Zashiki warashi are spirits that brings wealth and happiness to the household, and Nonono is here to bring prosperity to the Horikoshi family too....by blessing Tsuyuko with many offsprings?