For the full backstory before watching the movie, viewers should watch the two specific tie-in episodes available on platforms like Crunchyroll :
This episode is part of the "Uta's Past Arc," a mini-filler arc designed to provide context for the relationship between Luffy, Shanks, and the film's central character, Uta. One Piece Film: Red Episodio 1
Despite their bickering, they spend the day together in Windmill Village, competing in games and discovering a mutual love for freedom and adventure. For the full backstory before watching the movie,
Set approximately 12 years before the main story starts, before Luffy receives his signature eye scar or the straw hat from Shanks. This episode highlights why Luffy became so adamant
This episode highlights why Luffy became so adamant about having a musician on his crew later in life—a direct result of his early admiration for Uta’s singing. Recommended Watching Order
"A Faint Memory! Luffy and Red-Haired's Daughter Uta!"