Mama wa Shougaku 4-nensei

Because her father is relocated to London for work, Natsumi, a fourth-grade student, must also move from Japan to join him. Her classmates organize a farewell party in her honor. Natsumi prepares herself for the move to London, but on the night before her scheduled departure, a baby suddenly appears in her house following a loud clap of thunder! Even more astonishingly, this baby is actually the child that Natsumi will have fifteen years in the future! (Source: Aku Tenshi)