Natsumi Mizuki is a 4th grader whose parents have gone to London. Her Aunt Izumi comes to live with her. Izumi is an aspiring manga writer who is trying to get her first big break, so she doesn't have time for a baby that appears out of thin air on Natsumi's first night alone. The baby's name is Mirai and her mother is *Natsumi*, but 15 years older. Somehow, Mirai had traveled back in time. Now the young Natsumi has to raise Mirai while trying to keep her 4th grade life from falling apart and keep Mirai-chan secret from everyone. She has the dubious help of Izumi and some baby-care gadgets from the future.
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(Source: Anime News Network)

Because her father was sent to London to work, Natsumi, a 4th grade student, also must leave Japan along with him. Her classmates throw a farewell party for her. Natsumi is prepared to go to London, but on the night before Natsumi's arranged departure, a baby suddenly appears in her house after a roar of thunder! What's more is that this little baby is actually the one that Natsumi will give birth to in fifteen years!<br><br>
(Source: Aku Tenshi)