Basic Trope: The story begins with someone who's not the actual protagonist; he'll be coming in later.
Straight: In the Humongous Mecha anime Trope Busters, the story revolves around Bash the pilot of the titular mecha, and his fight against Emperor Evulz' evil empire. However, in episode 5, Bash makes a Heroic Sacrifice to stop The Dragon Triskelatus. From episode 6 onward, the pilot and the center of the story is Bob, Bash' adopted little brother.
Exaggerated: Something like this happens often in Trope Busters, when the 24-episodes anime ended, the titular mecha has been piloted by a dozen or so pilot, some of them doesn't even last half an episode. But each of them is a protagonist of their own story arc.
Downplayed:
Trope Busters is The Anime of the Game - in the game, you control five characters. However, one of them is a Guest Star Party Member and is replaced later on with another more significant character.
Halfway through the first season, Bash is Put on a Bus and replaced by Bob.
Subverted: In episode 17, Bash is Back from the Dead and is now ready to pilot the Trope Busters again. The story again revolves around him and his much-surprised friends and foes.
Parodied: Bash is a traditional cape-wearing, charismatic hero who is first seen delivering a speech to his fellow pilots about the importance of bravery and teamwork...right before being gunned down by a bunch of Mooks less than five minutes into the first episode.
Deconstructed:
La Résistance have a hard time coping with Bash' death.
Bob does his best to surpass Bash in every way, and he succeeds.
Zig Zagged: We see that Bash dies at the hand of Triskelatus, but some episodes after that we see that Bash is alive and kicking the arses of The Empire. It seems that Bash is still alive after all, just not fighting alongside Bob. But then it's revealed that those episodes are about Bash' past. But in one of those episode, we see adult Bob fighting alongside Bash. The episode right after that we see the very same adult Bob visiting the worn-out grave of Bash...
Averted: Bash is the protagonist of Trope Busters, from the first episode to the last.
Enforced: "We want to make a coming of age story of Bob. Bash's death give the audience a sense of passage of time."
Lampshaded:
'Bob: Bash kicks the bucket and you all assume I'm best for the job? You're out of your minds! Bash is the only one any good at this sort of thing!
Invoked:
'Alice: You are now the leader of La Résistance, Bob. It's your story, not Bash's.
Exploited: Bash trained Bob ahead of time, knowing that, eventually, he'd get himself killed, and didn't want to leave without knowing someone could continue his legacy.