Rabbit on the Moon (2007)

Sanae is a thirteen-year-old girl who lives with her mother and six-year-old sister. She has not recently been able to be open with her fisherman grandfather. Sanae is awoken by the sound of hard rain one night. As she dozes, the rain changes into the flow of the river and she finds herself lying in a fishing boat when she opens her eyes. She hears, from far away, the strains of a harmonica which her grandpa loves... Next morning Sanae is informed that her grandfather has passed away. Frictions are revealed between Sanae and those around her. In her confused state, she runs out of the house leaving for the river where her grandpa's boat is moored...

Unfortunately the movie Rabbit on the Moon is not yet available on HBO Max.