Luca is inspired by Enrico Casarosa’s own childhood living in the Italian Riviera and his experiences with his best friend (aside from the whole sea monster bit). Casarosa was much like Luca, more afraid and reserved, whilst his friend was daring and bold like Alberto. As the director shared with us, the ending of Luca actually came about when he was talking to his real best friend about the importance of friendship, including the cycle of growing apart. Casarosa expanded on reaching the finale to CinemaBlend (also in the video above):