(lit. "Mama is a 4th Grader) a Japanese shōjo anime by Sunrise. The 51-episode series was first aired from January 10, 1992 through December 25, 1992.In the year 2007 a woman is preparing for a party, while her husband is tinkering with a communication device for their new baby. A sudden lightning bolt affects the television, causing the baby to levitate and vanish.

In the year 1992, a 4th grader named Natsumi Mizuki is separated from her parents for a day, because her father's company only bought 2 tickets for their move to England, so they had to buy her a ticket for the following day. She is upset because her parents gave away her pet dog. Her aunt Izumi (her mother's younger sister), an aspiring manga writer, comes to live with Natsumi. They do not get along very well, with Natsumi calling her 'Oba-san' (Auntie) instead of 'Onee-san' (Big sis) as she would prefer.

While watching a movie, the baby appears in front of Natsumi. She becomes determined to raise the baby, not wanting to trust her with the clumsy policeman.

Through the strange heart-shaped device, Natsumi and Izumi learn that the baby's mother is Natsumi Mizuki from the year 2007! She is a married 24-year-old, and pleads with her past self to take care of the baby until they can determine how to return her. The device is also linked with a clasp around the baby's neck that notifies Izumi when the baby needs her, through transmitting her emotional state. Natsumi and Izumi continue to quarrel over how to raise the baby, and worry about time paradoxes that could occur.

Natsumi must now try to raise her future daughter, attend school, and foil her aunt's attempts to foist the baby onto other caregivers. Izumi is pressured into watching the baby while Natsumi is at school, in exchange for free board, since she lost her apartment. During this time, she tries to focus on creating her manga without distractions. Will she succeed in fifteen years?