Little DJ (2007)

Taro is a 12-year-old into baseball and radio, especially "Music Express," a song-request show. Sound quaint? But it is 1977 and a small town in Hokkaido, a more innocent, pure-hearted time and place, we are told. Taro, however, has a blood disease that lands him in the hospital where his aunt is a nurse. Rounds of tests, transfusions and injections sap his spirit, despite the kindness and dedication of his young doctor and the Doctor's hospital-director father. The latter, a music buff who broadcasts classics over the hospital's PA system, asks Taro to relieve him as DJ — and soon the boy is ensconced in the hospital director's well-stocked library-cum-studio, spinning popular J-Pop tunes. He also becomes acquainted with Tamaki, a girl he first calls "the mummy" because of her bandages and full body cast — she was injured in a traffic accident. He later changes his tune when she is revealed as a cute 13-year-old — for him, an older woman...

Unfortunately the movie Little DJ is not yet available on HBO Max.