Zense Reitetsu Ouji No Uma Deshita - Hito Ni Natte Mo Anata Wo Aishite Ii Desu Ka? summary:

When I woke up, I, a horse, had the body of a human!? I was Lukania, the beloved horse of the lonely second prince, Ladius. However, I lost my life in an attack aimed at Ladius."Until the day of brightness, guide him from the brink of despair—,” given power by a goddess and reborn as a human, Lukania heads toward Ladius. He rejects the kindness around him and believes that Luccanya, who disappeared, is still alive, and continues searching. Amidst the darkness of loneliness."I'll make you smile,” Luccanya decides to hide her past as a horse and vows to rescue Ladius from his loneliness within her limited time.