Subaru

A small five-year-old girl named Subaru no longer has time for friends and play. Why is this? Her twin brother Kazuma is dying...and gradually forgetting everything. Even Subaru. And so the girl visits him every day, talking with him and dancing for him, trying to make him remember her. And he always does by the end of the day. Encouraged by a friend to join ballet classes, the girl does so and falls in love with the dance.

(Source: Aerie Scans)

Subaru was adapted as a live-action film in 2009.