[The Promised Neverland] Watch the video! A movie adaptation!? Introducing the main character of the original novel, who was not mentioned in the anime.
In Dragon Quest: The Adventures of Dai, it's gotta be Pop! In Hunter x Hunter, it's Kurapika! A hidden hero who overshadows the main character is so cool! Speaking of which, in Yakuneba, it has to be this guy! But wait, wait!? That hugely popular character from the original doesn't appear in the anime!?