Namidaame to Serenade

On rainy days, Hina has dreams about her younger self playing with a mysterious boy in a garden she's never seen before—until, by chance, she stumbles upon the place. There's a young man there, Takaaki, who mistakes Hina for his fiancée Hinako. He whisks her back to what he thinks is her home, where Hina's doppelganger is waiting, and Hina realizes this isn't the Tokyo she left behind but Japan in the year 1907! Is this all a dream or something much stranger?