Change of protagonist or late entry of protagonist In all the manga that I have read and anime I have watched, the protagonist always appears in the first chapter of manga or first episode of an anime. 

Most of the time without reading the plot we can tell who is the protagonist after watching only a few episodes.

So my question: 

Has it ever happened that there any anime or manga where: 


The character who we think is the protagonist turns into a supporting character and another character turn into the protagonist
The protagonist appears or debuts later than 1 or 2 chapters or episodes.


But not including where the protagonist dies and there arises another protagonist.

And while providing an example try to mention which type of plot as mentioned above
Yes, there are. TV Tropes refers to this as a Decoy Protagonist, although TV Tropes' definition generally seems to refer to when the apparent main character gets killed early on in the series. Some examples of this may include Gurren Lagann, Yuru-Yuri, and Bokurano (I took these straight from the examples page and have not actually watched the latter two).