The Big First-Grader and the Small Second-Grader (2014)

First-grader Masaya is a crybaby despite his large stature, so he can't walk by himself on the dark path to school. The one who holds his hand is Akiyo, a tiny but capable second-grader. Masaya wants to be strong like Akiyo and admires her, but one day, something happens that leaves Akiyo in tears. To lift Akiyo's spirits, Masaya goes trekking to the distant Ipponsugi forest to find the spotted bellflowers that Akiyo loves.

Unfortunately the movie The Big First-Grader and the Small Second-Grader is not yet available on HBO Max.