Tokyo Boy (2008)

Minato is a young girl who was traumatized at a young age by being abandoned by her parents and left with her senile grandmother. She frequently corresponds with a pen-pal named Night, a boy about the same age as her that she's never actually seen in person. Although Minato and Night are very different - Minato is upbeat while Night is brooding, they get along anyway and she regularly updates him on the happenings in her daily life. Minato is even willing to confide in Night that she's falling in love with a boy she's recently met named Sho.

Unfortunately the movie Tokyo Boy is not yet available on HBO Max.