Mama is a 4th Grader(1992)

Mama is a 4th Grader is a Japanese comedy series about Natsumi Mizuki, a fourth-grader left in her aunt's care when her parents travel to London. Her life turns upside down when a baby mysteriously appears—Mirai, who is actually Natsumi herself from fifteen years in the future, somehow sent back in time. Now Natsumi must secretly raise her infant future self while juggling school, friendships, and keeping Mirai hidden from everyone around her. With help from her scattered manga-writing aunt Izumi and futuristic baby gadgets, Natsumi navigates the chaos of unexpected motherhood. The series blends heartfelt family moments with humor as a fourth-grader discovers what it takes to care for a baby while protecting her own childhood.